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1\documentclass[a4paper,11pt]{article}
2\usepackage{isolatin1,times,epsfig}
3\hyphenation{Message-Router Text-Query}
4
5\newenvironment{gsc}% Greenstone text bits
6{\begin{footnotesize}\begin{tt}}%
7{\end{tt}\end{footnotesize}}
8 
9\newcommand{\gst}[1]{{\footnotesize \tt #1}}
10
11\newcommand{\gsii}{Greenstone2}
12\newcommand{\gsiii}{Greenstone3}
13\newcommand{\gs}{Greenstone}
14
15\begin{document}
16
17\title{\gsiii\ : A modular digital library.}
18
19% if you work on this manual, add your name here
20\author{Katherine Don \\[1ex]
21        Department of Computer Science \\
22        University of Waikato \\ Hamilton, New Zealand \\ }
23
24\date{}
25
26\maketitle
27
28\newenvironment{bulletedlist}%
29{\begin{list}{$\bullet$}{\setlength{\itemsep}{0pt}\setlength{\parsep}{0pt}}}%
30{\end{list}}
31
32\noindent
33Greenstone Digital Library Version 3 is a complete redesign and
34reimplementation of the \gs\  digital library software.  The current
35version (\gsii) enjoys considerable success and is being widely used.
36\gsiii \  will capitalize on this success, and in addition it will
37\begin{bulletedlist}
38\item improve flexibility, modularity, and extensibility
39\item lower the bar for ``getting into'' the \gs\  code with a view to
40   understanding and extending it
41\item use XML where possible internally to improve the amount of
42   self-documentation
43\item make full use of existing XML-related standards and software
44\item provide improved internationalization, particularly in terms of sort order,
45   information browsing, etc.
46\item include new features that facilitate additional ``content management''
47   operations
48\item operate on a scale ranging from personal desktop to corporate library
49\item easily permit the incorporation of text mining operations
50\item use Java, to encourage multilinguality, X-compatibility, and to permit
51   easier inclusion of existing Java code (such as for text mining).
52\end{bulletedlist}
53Parts of \gs\  will remain in other languages (e.g. MG, MGPP); JNI (Java
54Native Interface) will be used to communicate with these.
55
56A description of the general design and architecture of \gsiii\  is covered by the document {\em The design of Greenstone3: An agent based dynamic digital library} (design-2002.ps, in the docs/manual directory).
57
58This documentation consists of several parts. Section~\ref{sec:install} is for administrators, and covers \gsiii\  installation, how to access the library, and some administration issues. Section~\ref{sec:user} is for users of the software, and looks at using the sample collections, creating new collections, and how to make small customizations to the interface. The remaining sections are aimed towards  the \gs\  developer. Section~\ref{sec:develop-runtime} describes the run-time system, including the structure of the software, and the message format. Section~\ref{sec:new-features} describes how to add new features to \gs, such as how to add new services, new page types, new plugins for different document formats.  Section~\ref{sec:distributed} describes how to make \gs\  run in a distributed fashion, using SOAP as an example communications protocol. Finally, there are several appendices, including how to install \gs\  from CVS, some notes on Tomcat and SOAP, and a comparison of \gsii\  and \gsiii\  format statements.
59\newpage
60\tableofcontents
61\newpage
62\section{\gs\  installation and administration}\label{sec:install}
63
64This section covers where to get \gsiii\  from, how to install it and how to run it. The standard method of running \gsiii\  is as a Java servlet. We provide the Tomcat servlet container to run the servlet. Standard web servers may  be able to be configured to provide servlet support, and thereby remove the need to use Tomcat. Please see your web server documentation for this. This documentation assumes that you are using Tomcat. To access \gsiii, Tomcat must be started up, and then it can be accessed via a web browser.
65
66Ant (Java's XML based build tool) is used for compilation, installation and running Greenstone. The \gst{build.xml} file is the configuration file for the Greenstone project, and \gst{build.properties} contains parameters that can be altered by the user.
67
68\subsection{Get and install \gs\ }\label{sec:getandinstall}
69
70\gsiii\  is available for download from Sourceforge:\\
71 \gst{https://sourceforge.net/projects/greenstone3}. There are Windows, Linux, and source releases. The binary releases are self-installing executables: download and run the file to install. A series of prompts will guide you through the installation process. The source release is a gzip'd tar file. Unzip and untar this, check build.properties, then run \gst{'ant install'} to configure and compile the code.
72
73The \gsiii\  library can be launched by running the server program. This is accessible from the Start menu on Windows, or by running the \gst{gs3-server.sh/bat} script in the top level \gst{greenstone3} directory. This program will start up the Tomcat web server and launch a browser.
74
75Alternatively, you can start it up using Ant: run \gst{'ant start'}, which starts up Tomcat, then in a browser go to \gst{http://localhost:8080/greenstone3}\\
76(or \gst{http://your-computer-name:your-chosen-port/greenstone3}). \\
77This gets you to a welcome page containing links to four servlets: the \gst{test} servlet (this allows you to check that Tomcat is running properly); the standard \gst{library} servlet which serves \gst{localsite} site with the \gst{gs2} interface; the \gst{gs3library} servlet which serves \gst{localsite} using the \gst{default} \gsiii-style interface; and the \gst{gateway} servlet, which serves \gst{gateway} site with the \gst{default} interface. The \gst{gateway} site uses a SOAP connection to communicate with \gst{localsite}, and demonstrates the library working in a distributed fashion. The SOAP connection is not enabled by default - to enable it, run \gst{'ant deploy-localsite'}.
78
79\gsiii\  is also available through CVS (Concurrent Versioning System). This provides the latest development version, and is not guaranteed to be stable. Appendix~\ref{app:cvs} describes how to download and install \gsiii\  from CVS.
80
81\subsection{How the library works}
82
83The standard library program is a Java servlet. We use the Tomcat servlet container to present the servlets over the web. Tomcat takes CGI-style URLs and passes the arguments to the servlet, which processes these and returns a page of HTML. As far as an end-user is concerned, a servlet is a Java version of a CGI program. The interaction is similar: access is via a web browser, using arguments in a URL.
84
85Other types of interfaces can be used, such as Java GUI programs. See Section~\ref{sec:new-interfaces} for details about how to make these.
86
87\subsubsection{Restarting the library}
88
89You can restart Tomcat by clicking 'Restart Server' on the little server program. You should restart the server any time you make changes in the following for those changes to take effect:\\
90\begin{bulletedlist}
91\begin{gsc}
92\item \$GSDL3HOME/WEB-INF/web.xml
93\item \$GSDL3SRCHOME/packages/tomcat/conf/server.xml
94\end{gsc}
95\item any classes or jar files used by the servlets
96\end{bulletedlist}
97
98
99\subsection{Directory structure}
100
101Table~\ref{tab:dirs} shows the file hierarchy for \gsiii.
102The first part  shows the common stuff which can be shared between
103\gs\  users---the source, libraries etc. The second part shows the file hierarchy for the web directory, which comprises the greenstone3 context for Tomcat, and is accessible via Tomcat. The main directories are for sites and interfaces: there can be several sites and interfaces per installation, and they are described in the following section.
104
105Two environment variables used by \gsiii\ are often mentioned in this manual: \gst{\$GSDL3SRCHOME} and \gst{\$GSDL3HOME}. \gst{\$GSDL3SRCHOME} refers to the top-level \gst{greenstone3} directory, while \gst{\$GSDL3HOME} refers to the \gst{web} directory. The web directory contains everything needed to serve the \gsiii\ library using Tomcat, and doesn't necessarily need to live with the rest of the \gsiii\ source.
106
107\begin{table}
108\caption{The \gs\  directory structure}
109\label{tab:dirs}
110{\footnotesize
111\begin{tabular}{l p{8cm}}
112\hline
113\bf directory & \bf description \\
114\hline
115greenstone3
116  & The main installation directory---\$GSDL3SRCHOME is set to this directory \\
117greenstone3/src
118  & Source code lives here \\
119greenstone3/src/java/
120  & main \gsiii\  java source code \\
121greenstone3/src/packages
122  & Imported source packages from other systems e.g. indexing packages may go here \\
123greenstone3/lib
124  & Shared library files\\
125greenstone3/lib/java
126  & Java jar files not needed in the \gsiii\  runtime\\
127greenstone3/lib/jni
128  & Jar files and shared library files (.so, .jnilib, .dll) needed for JNI components \\
129greenstone3/resources
130 & any resources that may be needed\\
131greenstone3/resources/soap
132 & soap service description files \\
133greenstone3/bin
134  & executable stuff lives here\\
135greenstone3/bin/script
136  & some Perl and/or shell scripts\\
137greenstone3/packages
138  & External packages that may be installed as part of greenstone, e.g. Tomcat \\
139greenstone3/docs
140  & Documentation\\
141greenstone3/gli
142  & \gs\ Librarian Interface code \\
143greenstone3/gs2build
144  & collection building code\\
145\hline
146greenstone3/web
147  & This is where the web site is defined. Any static HTML files can go here. This directory is the root directory used by Tomcat when serving \gsiii. \$GSDL3HOME is set to this directory. \\
148greenstone3/web/WEB-INF
149  & The web.xml file lives here (servlet configuration information for Tomcat)\\
150greenstone3/web/WEB-INF/classes
151  & Individual class files needed by the servlet go in here, also properties files for java resource bundles - used to handle all the language specific text. This directory is on the servlet classpath\\
152greenstone3/web/WEB-INF/lib
153  & jar files needed by the servlets go here \\
154greenstone3/web/sites
155  & Contains directories for different sites---a site is a set of collections and services served by a single MessageRouter (MR). The MR may have connections (e.g. soap) to other sites\\
156greenstone3/web/sites/localsite
157  & An example site - the site configuration file lives here\\
158greenstone3/web/sites/localsite/collect
159  & The collections directory \\
160greenstone3/web/sites/localsite/images
161  & Site specific images \\
162greenstone3/web/sites/localsite/transforms
163  & Site specific transforms \\
164greenstone3/web/interfaces
165  & Contains directories for different interfaces - an interface is defined by its images and XSLT files \\
166greenstone3/web/interfaces/default
167  & The default interface\\
168greenstone3/web/interfaces/default/images
169  & The images for the default interface\\
170greenstone3/web/interfaces/default/js
171  & The javascript libraries for the default interface\\
172greenstone3/web/interfaces/default/style
173  & The CSS stylesheets for the default interface\\
174greenstone3/web/interfaces/default/transforms
175  & The XSLT files for the default interface\\
176greenstone3/web/applet
177  & jar files needed by applets can go here \\
178\hline
179\end{tabular}}
180\end{table}
181
182
183\subsection{Sites and interfaces}\label{sec:sites-and-ints}
184
185Sites and interfaces contain the content and presentation information, respectively, for the digital library.
186A site is comprised of a set of collections and possibly some site-wide services. An interface (in this web-based servlet context) is a set of images along with a set of XSLT files used for translating xml output from the library into an appropriate form---HTML in general.
187
188One \gsiii\  installation can have many sites and interfaces, and these can be paired in different combinations.  One instantiation of a servlet uses one site and one interface, so every specified pairing results in a new servlet instance.  For example, a single site might be served with two different interfaces. This provides different modes of access to the same content. e.g. HTML vs WML, or perhaps providing a completely different look and feel for different audiences. Alternatively, a standard interface may be used with many different sites---providing a consistent mode of access to a lot of different content.
189
190Collections live in the \gst{collect} directory of a site. Any collections that are found in this directory when the servlet is initialized will be loaded up. Public collections will appear on the library home page, while private collections will be hidden. These can still be accessed by typing in cgi arguments. Collections require valid configuration files, but apart from this, nothing needs to be done to the site to use new collections. Collections added while Tomcat is running will not be noticed automatically. Either the server needs to be restarted, or a configuration request may be sent to the library, triggering a (re)load of the collection (this is described in Section~\ref{sec:runtime-config}).
191
192There are two  sites that come with the distribution: \gst{localsite}, and \gst{gateway}. \gst{localsite} has several demo  collections, while \gst{gateway} has none. \gst{gateway} specifies that a SOAP connection should be made to \gst{localsite}. Getting this to work involves setting up a soap server for localsite: see Section~\ref{sec:distributed} for details.
193There are also two interfaces provided in the distribution: \gst{default} and \gst{gs2}. The default interface is a generic \gsiii\ interface, while the \gst{gs2} interface aims to look like the old \gsii\ interface.
194
195Each site and interface has a configuration file which specifies parameters for the site or interface---these are described in Section~\ref{sec:config}.
196
197\subsection{Configuring Tomcat}\label{sec:tomcat-config}
198
199The file \gst{\$GSDL3HOME/WEB-INF/web.xml} contains the configuration information for Tomcat. It tells Tomcat what servlets to load, what initial parameters to pass them, and what web names map to the servlets.
200There are four servlets specified in web.xml (these correspond to the four servlet links in the welcome page for \gsiii): one is a test servlet that just prints ``hello greenstone'' to a web page. This is useful if you are having trouble getting Tomcat set up. The other three are the \gs\  library servlets described in Section~\ref{sec:getandinstall}, \gst{library}, \gst{gs3library} and \gst{gateway}. Each servlet must specify which site and which interface to use. Having multiple servlets provides a way of serving different sites, or the same site with a different style of presentation. \gst{site\_name} and \gst{interface\_name} are just two examples of initialization parameters used by the library servlets. The full list is shown in Table~\ref{tab:serv-init}.
201
202For more details about Tomcat see Appendix~\ref{app:tomcat}.
203
204\begin{table}
205\caption{\gs\  servlet initialization parameters}
206\label{tab:serv-init}
207{\footnotesize
208\begin{tabular}{lp{3.5cm}p{6cm}}
209\hline
210\bf name & \bf sample value & \bf description \\
211\hline
212library\_name & library & the web name of the servlet \\
213interface\_name & default & the name of the interface to use\\
214site\_name & localsite & the name of the local site to use (use either site\_name or the three remote\_site parameters)\\
215remote\_site\_name & org.greenstone.site1 & the name of a remote site (can be anything??) \\
216remote\_site\_type & soap & the type of server running on the site \\
217remote\_site\_address & http://www.greenstone.org/ greenstone3/services/ localsite & The address of the server \\
218default\_lang & en & the default language for the interface\\
219receptionist\_class & MyReceptionist & (optional) specifies an alternative Receptionist to use (default is DefaultReceptionist)\\
220messagerouter\_class & NewMessageRouter & (optional) specifies an alternative MessageRouter to use (default is MessageRouter)\\
221params\_class & GS2Params & (optional) specifies an alternative GSParams class to use \\
222\hline
223\end{tabular}}
224\end{table}
225
226\subsection{Configuring a \gs\ library}\label{sec:config}
227
228Initial \gsiii\  system configuration is determined by a set of XML configuration files. Each site has a configuration file that binds parameters for the site, \gst{siteConfig.xml}. Each interface has a configuration file, \gst{interfaceConfig.xml}, that specifies parameters for the interface. Collections also have several configuration files; these are discussed in Section~\ref{sec:collconfig}.
229The configuration files are read in when the system is initialized, and their contents are cached in memory. This means that changes made to these files once the system is running will not take immediate effect. Tomcat needs to be restarted for changes to the interface configuration file to take effect. However, changes to the site configuration file can be incorporated sending a system command to the library.  There are a series of system commands that can be sent to the library to induce reconfiguration of different modules, including reloading the whole site. This removes the need to restart the system to reflect these changes. These commands are described in Section~\ref{sec:runtime-config}.
230
231\subsubsection{Site configuration file}\label{sec:siteconfig}
232
233The file \gst{siteConfig.xml} specifies the URI for the site (\gst{localSiteName}), the HTTP address for site resources (\gst{httpAddress}), any \gst{ServiceClusters} that the site provides (for example, collection building), any \gst{ServiceRacks} that do not belong to a cluster or collection, and a list of
234known external sites to connect to.  Collections are not specified in the site
235configuration file, but are determined by the contents of the site's
236collect directory.
237
238The HTTP address is used for retrieving resources from a site outside the XML protocol. Because a site is HTTP accessible through Tomcat, any files (e.g. images) belonging to that site or to its collections can be specified in the HTML of a page by a URL. This avoids having to retrieve these files from a remote site via the XML protocol\footnote{Currently, sites live inside the Tomcat greenstone3 root context, and therefore all their content is accessible over HTTP via the Tomcat address. We need to see if parts can be restricted. Also, if we use a different protocol, then resources from remote sites may need to come through the XML. Also, if we are running locally without using Tomcat, we may want to get them via file:// rather than http://.}.
239 
240Figure~\ref{fig:siteconfig} shows two example site configuration files. The first example is for a rudimentary site with no site-wide services,
241which does not connect to any external sites. The second example is for a site with one site-wide service cluster - a collection building cluster.  It also connects to the first site using SOAP.
242These two sites happen to be running on the same machine, which is why they can use \gst{localhost} in the address. For site \gst{gsdl1} to talk to site \gst{localsite}, a SOAP server must be run for \gst{localsite}. The address of the SOAP server, in this case, is \gst{http://localhost:8080/greenstone3/services/localsite}.
243
244
245\begin{figure}
246\begin{gsc}\begin{verbatim}
247<siteConfig>
248  <localSiteName value="org.greenstone.localsite"/>
249  <httpAddress value="http://localhost:8080/greenstone3/sites/localsite"/>
250  <serviceClusterList/>
251  <serviceRackList/>
252  <siteList/>
253</siteConfig>
254\end{verbatim}\end{gsc}
255
256\begin{gsc}\begin{verbatim}
257<siteConfig>
258  <localSiteName value="org.greenstone.gsdl1"/>
259  <httpAddress value="http://localhost:8080/greenstone3/sites/gsdl1"/>
260  <serviceClusterList> 
261    <serviceCluster name="build">
262      <metadataList>
263        <metadata name="Title">Collection builder</metadata>
264        <metadata name="Description">Builds collections in a
265           gsdl2-style manner</metadata>
266      </metadataList>
267      <serviceRackList>
268        <serviceRack name="GS2Construct"/>
269      </serviceRackList>
270    </serviceCluster>
271  </serviceClusterList>
272  <siteList>
273    <site name="org.greenstone.localsite"
274      address="http://localhost:8080/greenstone3/services/localsite"
275      type="soap"/>
276  </siteList>
277</siteConfig>
278\end{verbatim}\end{gsc}
279\caption{Two sample site configuration files}
280\label{fig:siteconfig}
281\end{figure}
282
283Another element that can appear in a site configuration file is \gst{replaceList}. This must have an \gst{id} attribute, and may contain one or more \gst{replace} elements. Replace elements are discussed in Section \ref{sec:collconfig}. The list found in a \gst{siteConfig.xml} file can be applied to any collection by adding a \gst{replaceListRef} element (with the appropriate \gst{id} attribute) to its \gst{collectionConfig.xml} file.
284
285\subsubsection{Interface configuration file}\label{sec:interfaceconfig}
286
287The interface configuration file \gst{interfaceConfig.xml} lists all the actions that the interface knows about at the start (other ones can be loaded dynamically). Actions create the web pages for the library: there is generally one Action per type of page. For example, a query action produces the pages for searching, while a document action displays the documents. The configuration file specifies what short name each action maps to (this is used in library URLs for the a (action) parameter) e.g. QueryAction should use \gst{a=q}. If the interface uses XSLT, it specifies what XSLT file should be used for each action and possibly each subaction. This makes it easy for developers to implement and use different actions and/or XSLT files without recompilation. The server must be restarted, however.
288
289It also lists all the languages that the interface text files have been translated into. These have a \gst{name} attribute, which is the ISO code for the language, and a \gst{displayElement} which gives the language name in that language (note that this file should be encoded in UTF-8). This language list is used on the Preferences page to allow the user to change the interface language. Details on how to add a new language to a \gsiii\  library are shown in Section~\ref{sec:interface-language}.
290
291An \gst{optionList} element can be used to disable or enable some optional functionality for the interface. Currently there are three options that can be enabled:
292
293\begin{tabular}{lp{7cm}}
294highlightQueryTerms & Whether search term highlighting is available or not\\
295berryBaskets & Whether berry basket functionality is available or not\\
296displayAnnotationService & Whether any annotation services (specified in the site config file) should be displayed with a document or not. \\
297\end{tabular}
298
299An interface may be based on an existing one, for example, the gs2 interface is based on the default interface. This means that it will use any images or templates from the base one unless overridden in the current one. The \gst{baseInterface} attribute of the \gst{<interfaceConfig>} element is used to specify the base interface.
300 
301\begin{figure}
302\begin{gsc}\begin{verbatim}
303<interfaceConfig>
304  <actionList>
305    <action name='p' class='PageAction'>
306      <subaction name='home' xslt='home.xsl'/>
307      <subaction name='about' xslt='about.xsl'/>
308      <subaction name='help' xslt='help.xsl'/>
309      <subaction name='pref' xslt='pref.xsl'/>
310      <subaction name='nav' xslt='nav.xsl'/><!-- used for the
311            collection header frame -->
312      <subaction name="html" xslt="html.xsl"/> <!-- used to put an
313            external page into a frame with a collection header-->
314    </action>
315    <action name='q' class='QueryAction' xslt='basicquery.xsl'/>
316    <action name='b' class='GS2BrowseAction' xslt='classifier.xsl'/>
317    <action name='a' class='AppletAction' xslt='applet.xsl'/>
318    <action name='d' class='DocumentAction' xslt='document.xsl'/>
319    <action name='xd' class='XMLDocumentAction'>
320      <subaction name='toc' xslt='document-toc.xsl'/>
321      <subaction name='text' xslt='document-content.xsl'/>
322    </action>
323    <action name='pr' class='ProcessAction' xslt='process.xsl'/>
324    <action name='s' class='SystemAction' xslt='system.xsl'/>
325    <action name='g' class='GeneralAction'>
326      <subaction name="berry" xslt='berry.xsl'/>
327    </action>
328  </actionList>
329  <languageList>
330    <language name="en">
331      <displayItem name='name'>English</displayItem>
332    </language>
333    <language name="fr">
334      <displayItem name='name'>Français</displayItem>
335    </language>
336    <language name='es'>
337      <displayItem name='name'>Español</displayItem>
338    </language>
339  </languageList>
340  <optionList>
341    <option name="highlightQueryTerms" value="true"/>
342    <option name="berryBaskets" value="true"/>
343  </optionList>
344</interfaceConfig>
345\end{verbatim}\end{gsc}
346\caption{Default interface configuration file}
347\label{fig:ifaceconfig}
348\end{figure}
349
350
351\subsection{Run-time re-initialization}\label{sec:runtime-config}
352
353When Tomcat is started up, the site and interface configuration files are read in, and actions/services/collections loaded as necessary. The configuration is then static unless Tomcat is restarted, or re-configuration commands issued.
354
355There are several commands that can be issued to Tomcat to avoid having to restart the server. These can reload the entire site, or just individual collections. Unfortunately at present there are no commands to reconfigure the interface, so if the interface configuration file has changed, Tomcat must be restarted for those changes to take effect. Similarly, if the Java classes are modified, Tomcat must be restarted then too.
356
357Currently, the runtime configuration commands can only be accessed by typing arguments into the URL; there is no nice web form yet to do this.
358
359The arguments are entered after the \gst{library?} part of the URL. There are three types of commands: configure, activate, deactivate. These are specified by \gst{a=s\&sa=c}, \gst{a=s\&sa=a}, and \gst{a=s\&sa=d}, respectively (\gst{a} is action, \gst{sa} is subaction). By default, the requests are sent to the MessageRouter, but they can be sent to a collection/cluster by the addition of \gst{sc=xxx}, where \gst{xxx} is the name of the collection or cluster. Table~\ref{tab:run-time config} describes the commands and arguments in a bit more detail.
360
361\begin{table}
362\caption{Example run-time configuration arguments.}
363\label{tab:run-time config}
364{\footnotesize
365\begin{tabular}{lp{9cm}}
366\hline
367\gst{a=s\&sa=c} & reconfigures the whole site. Reads in siteConfig.xml, reloads all the collections. Just part of this can be specified with another argument \gst{ss} (system subset). The valid values are \gst{collectionList}, \gst{siteList}, \gst{serviceList}, \gst{clusterList}. \\
368\gst{a=s\&sa=c\&sc=XXX} & reconfigures the XXX collection or cluster. \gst{ss} can also be used here, valid values are \gst{metadataList} and \gst{serviceList}. \\
369\gst{a=s\&sa=a} & (re)activate a specific module. Modules are specified using two arguments, \gst{st} (system module type) and \gst{sn} (system module name). Valid types are \gst{collection}, \gst{cluster} \gst{site}.\\
370\gst{a=s\&sa=d} & deactivate a module. \gst{st} and \gst{sn} can be used here too. Valid types are \gst{collection}, \gst{cluster}, \gst{site}, \gst{service}. Modules are removed from the current configuration, but will reappear if Tomcat is restarted.\\
371\gst{a=s\&sa=d\&sc=XXX} & deactivate a module belonging to the XXX collection or cluster. \gst{st} and \gst{sn} can be used here too. Valid types are \gst{service}. \\
372\hline
373\end{tabular}}
374\end{table}
375\newpage
376\section{Using \gsiii\ }\label{sec:user}
377
378Once \gsiii\ is installed, the sample collections can be accessed. The installation comes with several example collections, and Section~\ref{sec:usecolls} describes these collections and how to use them. Section~\ref{sec:buildcol} describes how to build new collections.
379
380\subsection{Using a collection}\label{sec:usecolls}
381
382A collection typically consists of a set of documents, which could be text, HTML, word, PDF, images, bibliographic records etc, along with some access methods, or ``services''. Typical access methods include searching or browsing for document identifiers, and retrieval of content or metadata for those identifiers.
383Searching involves entering words or phrases and getting back lists of documents that contain those words. The search terms may be restricted to particular fields of the document.
384
385Browsing involves navigating pre-defined hierarchies of documents, following links of interest to find documents. The hierarchies may be constructed on different metadata fields, for example, alphabetical lists of Titles, or a hierarchy of Subject classifications. Clicking on a bookshelf icon takes you to a lower level in the hierarchy, while clicking on a book or page icon takes you to a document.
386
387In the standard interface that comes with \gsiii\ \footnote{of course, this is all customizable}, collections in a digital library are presented in the following manner. The 'home' page of the library shows a list of all the public collections in that library. Clicking on a collection link takes you to the home page for the collection, which we call the collection's 'about' page. The standard page banner for a collection looks something like that shown in Figure~\ref{fig:page-banner}.
388
389\begin{figure}[h]
390  \centering
391  \includegraphics[width=4in]{pagebanner.ps} %5.8
392  \caption{A sample collection page banner}
393  \label{fig:page-banner}
394\end{figure}
395
396The image at the top left is a link to the collection's home page. The top right has buttons to link to the library home page, help and preferences pages. All the available services are arrayed along a navigation bar, along the bottom of the banner. Clicking on a name accesses that service.
397
398Search type services generally provide a form to fill in, with parameters including what field or granularity to search, and the query itself. Clicking the search button carries out the search, and a list of matching documents will be displayed. Clicking on the icons in the result list takes you to the document itself.
399
400Once you are looking at a document, clicking the open book icon at the top of the document, underneath the navigation bar, will take you back to the service page that you accessed the document from.
401
402\subsection{Building a collection}\label{sec:buildcol}
403
404There are three ways to get a new collection into \gsiii. The most common way is to use the Greenstone Librarian Interface to create a collection. If you have existing collections in a \gsii\ installation, these can be imported into \gsiii. Thirdly, you can use the Perl command line building scripts directly.
405
406Collections live in the \gst{collect} directory of a site. As described in Section~\ref{sec:sites-and-ints}, there can be several sites per \gsiii\  installation. The collect directory is at \gst{\$GSDL3HOME/sites/site-name/collect}, where site-name is the name of the site you want your new collection to belong to.
407
408The following three sections briefly  describe how to create a collection using GLI, how to import a collection from \gsii, and how to use command line building.  Once a collection has been built (and is located in the collect directory), the library server needs to be notified that there is a new collection. This can be accomplished in two ways\footnote{and eventually there will also probably be automatic polling for new collections}. If you are the library administrator, you can restart Tomcat. The library servlet will then be created afresh, and will discover the new collection when it scans the collect directory for the collection list. Alternatively, an activate collection command can be issued to the servlet, using the arguments \gst{a=s\&sa=a\&st=collection\&sn=collname}, where \gst{collname} should be replaced with the collection name---this tells the library program to (re)load the \gst{collname} collection.
409
410\subsubsection{Using the Librarian Interface}
411
412The Greenstone Librarian Interface (GLI) can be used to create collections. The procedure is the same as for \gsii, but it works in a \gsiii\  context. It can be started under Windows by selecting Greenstone Librarian Interface from the Greenstone 3 Digital Library menu in the Program Files section of the Start menu. On Linux, run \gst{ant gli} from the \gst{greenstone3} directory, or run \gst{./gli4gs3.sh} from the \gst{\$GSDL3SRCHOME/gli} directory.
413
414Currently, the GLI works almost exactly the same as for \gsii\footnote{Eventually the GLI will be modified to use \gsiii\ XML  configuration files.}. Collection configuration is done in a \gsii\ manner. The main difference is that \gsiii\ has different sites and interfaces and servlets, whereas \gsii\ has a single collect directory, and a single runtime cgi program.
415
416The GLI for \gsiii\ has a couple of new configuration parameters: site and servlet. It operates within a single site---you can edit, delete, and create new collections within this site. A servlet is also specified for that site---this is used when previewing a collection. While you are working in one site, you cannot edit collections from another site. However, you can base a collection on one from another site. To change the working site and/or servlet, go to Preferences-$>$Connection in the File menu. By default, the GLI will use site \gst{localsite}, and servlet \gst{library}.
417
418Collection building using the GLI will use the \gsii\ Perl scripts and plugins. At the conclusion of the \gsii\ build process, a conversion script will be run to create the \gsiii\  configuration files. This means that format statements are no longer 'live'---changing these will require changes to the \gsiii\ configuration files. Clicking the Preview Collection button will re-run the configuration file conversion script. If you change anything on the Format panel, you will need to click Preview Collection. Just reloading the collection via a browser will not be enough.
419 
420Detailed instructions about using the GLI can be found in Sections 3.1 and 3.2 of the \gsii\  User's Guide (\gst{GS2-User-en.pdf}). This can be found in  your \gsii\ installation, or in the \gst{\$GSDL3SRCHOME/docs/manual} directory if you have installed \gsiii\ from a distribution.
421
422
423\subsubsection{Importing from \gsii}
424
425Pre-built \gsii\ collections can also be used in \gsiii. The collection folder should be copied to the collect directory of the site it is to appear in (or a symbolic link may be used if possible).
426The \gsiii\  run time system requires different configuration files for a collection, so you need to run a conversion script. All this does is create the new \gst{collectionConfig.xml} and \gst{buildConfig.xml} from the old \gst{collect.cfg} and \gst{build.cfg} files. It does not change the collection in any way, so it can still be used by \gsii\  software.
427
428The conversion script is \gst{convert\_coll\_from\_gs2.pl}. To run it, make sure you have run \gst{source setup.bash} (or \gst{setup} in Windows) in the \gst{\$GSDL3SRCHOME/gs2build} directory (as well as running the standard \gst{gs3-setup} command). Then you need to specify the path to the collect directory and the collection name as parameters to the conversion script. For example,
429
430\begin{gsc}
431\begin{verbatim}
432convert_coll_from_gs2.pl -collectdir
433   $GSDL3HOME/sites/localsite/collect gs2mgdemo
434\end{verbatim}
435\end{gsc}
436%$
437The script attempts to create \gsiii\  format statements from the old \gsii\  ones. The conversion may not always work properly, so if the collection looks a bit strange under \gsiii, you should check the format statements. Format statements are described in Section~\ref{sec:formatstmt}.
438
439Once again, to have the collection recognized by the library servlet, you can either restart Tomcat, or load it dynamically.
440
441\subsubsection{Using command line building}
442
443This is the same procedure as for \gsii\ command line building, with the addition of a final step to create the \gsiii\ configuration files. The basic steps are (for a new collection called testcol):
444
445Linux:
446
447\begin{gsc}
448\begin{verbatim}
449cd greenstone3
450source gs3-setup.sh
451cd gs2build
452source setup.bash
453cd ../
454mkcol.pl -collectdir $GSDL3HOME/sites/localsite/collect testcol
455put source documents and metadata into
456            $GSDL3HOME/sites/localsite/collect/testcol/import
457edit $GSDL3HOME/sites/localsite/collect/testcol/etc/collect.cfg as
458            appropriate
459import.pl -collectdir $GSDL3HOME/sites/localsite/collect testcol
460buildcol.pl -collectdir $GSDL3HOME/sites/localsite/collect testcol
461rename the $GSDL3HOME/sites/localsite/collect/testcol/building
462            directory to index
463convert_coll_from_gs2.pl -collectdir $GSDL3HOME/sites/localsite/collect
464            testcol
465%$
466\end{verbatim}
467\end{gsc}
468
469Windows:
470\begin{gsc}
471\begin{verbatim}
472cd greenstone3
473gs3-setup
474cd gs2build
475setup
476cd ..
477perl -S mkcol.pl -collectdir %GSDL3HOME%\sites\localsite\collect testcol
478put source documents and metadata into
479            %GSDL3HOME%\sites\localsite\collect\testcol\import
480edit %GSDL3HOME%\sites\localsite\collect\testcol\etc\collect.cfg as
481            appropriate
482perl -S import.pl -collectdir %GSDL3HOME%\sites\localsite\collect testcol
483perl -S buildcol.pl -collectdir %GSDL3HOME%\sites\localsite\collect testcol
484rename the %GSDL3HOME%\sites\localsite\collect\testcol\building directory
485            to index
486perl -S convert_coll_from_gs2.pl -collectdir
487            %GSDL3HOME%\sites\localsite\collect testcol
488\end{verbatim}
489\end{gsc}
490
491Once the build process is complete, Tomcat should be prompted to reload the collection---either by restarting the server, or by sending an activate collection command to the library servlet.
492
493Metadata for documents can be added using \gst{metadata.xml} files.  A \gst{metadata.xml} file has a root element of \gst{<DirectoryMetadata>}.  This encloses a series of \gst{<FileSet>} items.  Neither of these tags has any attributes.  Each \gst{<FileSet>} item includes two parts: firstly, one or more \gst{<FileName>} tags, each of which encloses a regular expression to identify the files which are to be assigned the metadata.  Only files in the same directory as the \gst{metadata.xml} file, or in one of its child directories, will be selected.  The filename tag encloses the regular expression as text, e.g.:
494
495\begin{gsc}\begin{verbatim}
496<FileName>example</FileName>
497\end{verbatim}\end{gsc}
498
499This would match any file containing the text 'example' in its name.  The second part of the \gst{<FileSet>} item is a \gst{<Description>} item.  The \gst{<Description>} tag has no attributes, but encloses one or more \gst{<Metadata>} tags.  Each \gst{<Metadata>} tag contains one metadata item, i.e. a label to describe the metadata and a corresponding value.  The \gst{<Metadata>} tag has one compulsory attribute: \gst{'name'}.  This attribute gives the metadata label to add to the document.  Each \gst{<Metadata>} tag also has an optional attribute: \gst{'mode'}.  If this attribute is set to \gst{'accumulate'} then the value is added to the document, and any existing values for that metadata item are retained.  If the attribute is set to \gst{'set'} or is omitted, then any existing value of the metadata item will be deleted.
500
501\begin{figure}
502\begin{gsc}\begin{verbatim}
503<?xml version="1.0" encoding="UTF-8"?>
504<!DOCTYPE DirectoryMetadata SYSTEM "http://greenstone.org/dtd/DirectoryMetadata
505         /1.0/DirectoryMetadata.dtd">
506<DirectoryMetadata>
507  <FileSet>
508    <FileName>ec160e</FileName>
509    <Description>
510      <Metadata name="Title">The Courier - No.160 - Nov - Dec 1996 -
511         Dossier Habitat - Country reports: Fiji , Tonga (ec160e)</Metadata>
512      <Metadata mode="accumulate" name="Language">English</Metadata>
513      <Metadata mode="accumulate" name="Subject">Settlements and housing:
514        general works incl. low- cost housing, planning techniques, surveying,
515        etc.</Metadata>
516      <Metadata mode="accumulate" name="Subject">The Courier ACP 1990 - 1996
517        Africa-Caribbean-Pacific - European Union</Metadata>
518      <Metadata mode="accumulate" name="Organization">EC Courier</Metadata>
519      <Metadata mode="accumulate" name="AZList">T.1</Metadata>
520    </Description>
521  </FileSet>
522  <FileSet>
523    <FileName>b22bue</FileName>
524    <Description>
525      <Metadata name="Title">Butterfly Farming in Papua New Guinea
526        (b22bue)</Metadata>
527      <Metadata mode="accumulate" name="Language">English</Metadata>
528      <Metadata mode="accumulate" name="Subject">Other animals (micro-
529        livestock, little known animals, silkworms, reptiles, frogs,
530        snails, game, etc.)</Metadata>
531      <Metadata mode="accumulate" name="Organization">BOSTID</Metadata>
532      <Metadata mode="accumulate" name="AZList">T.1</Metadata>
533      <Metadata mode="accumulate" name="Keyword">start a butterfly farm
534        </Metadata>
535    </Description>
536  </FileSet>
537</DirectoryMetadata>
538\end{verbatim}\end{gsc}
539\caption{Sample metadata.xml file}
540\label{fig:metadatafile}
541\end{figure}
542
543Figure~\ref{fig:metadatafile} shows an example metadata.xml file.
544Here, only one file pattern is found in each file set.  However, the \gst{Description} tag contains a number of separate metadata items.  Note that the \gst{Title} metadata does not have the \gst{mode=accumulate} attribute.  This means that when this title is assigned to a document, any existing \gst{Title} information will be lost.
545
546
547\subsection{Collection configuration files}\label{sec:collconfig}
548
549Each collection has two, or possibly three, \gsiii\ configuration files, \\
550\gst{collectionConfig.xml}, \gst{buildConfig.xml}, and optionally \gst{collectionInit.xml}, that give metadata, display and other information for the
551collection. Currently, \gst{collectionConfig.xml} and \gst{buildConfig.xml} are generated from \gst{collect.cfg} and \gst{build.cfg}. At some stage, the collection building process and the Librarian Interface will be modified to use these files directly.
552\gst{collect.cfg} and/or \gst{collectionConfig.xml} includes user-defined presentation metadata for the collection, such as its name and the {\em About this collection} text; gives formatting information for the collection display; and also gives instructions on how the collection is to be built. \gst{build.cfg} and/or \gst{buildConfig.xml} are produced by the build-time process and include any metadata that can be determined automatically. It also includes configuration information for any ServiceRacks needed by the collection.
553
554All the configuration files should be encoded using UTF-8.
555
556The format of \gst{collect.cfg} and \gst{build.cfg} are not discussed here. Please see the \gsii\ manuals for more information regarding these files.
557
558\subsubsection{collectionInit.xml}
559
560This optional file is only used for non-standard, customized collections. It specifies the class name of the non-standard collection class.  The only syntax so far is the class name:
561
562\begin{gsc}\begin{verbatim}
563<collectionInit class="XMLCollection"/>
564\end{verbatim}\end{gsc}
565
566Section~\ref{sec:new-coll-types} describes an example collection where this file is used. Depending on the type of collection that this is used for, one or both of the other configuration files may not be needed.
567
568\subsubsection{collectionConfig.xml}
569
570The collection configuration file is where the collection designer (e.g. a librarian) decides what form the collection should take. So far this file only includes the presentation aspects needed by the run-time system. Instructions for collection building have yet to be defined. Presentation aspects include collection metadata such as title and description, display text for indexes, and format statements for search results, classifiers etc. The format of \gst{collectionConfig.xml} is still under consideration. However, Figure~\ref{fig:collconfig} shows the parts of it that have been defined so far.
571
572Display elements for a collection can be entered in any language---use \gst{lang='en'} attributes to specify which language they are in.
573
574\begin{figure}
575\begin{gsc}\begin{verbatim}
576<collectionConfig xmlns:gsf="http://www.greenstone.org/greenstone3/
577  schema/ConfigFormat" xmlns:xslt="http://www.w3.org/1999/XSL/Transform">
578  <metadataList>
579    <metadata name="creator">greenstone@cs.waikato.ac.nz</metadata>
580    <metadata name="public">true</metadata>
581  </metadataList>
582  <displayItemList>
583    <displayItem name='name' lang='en'>Greenstone3 MG demo collection</displayItem>
584    <displayItem name='description' lang='en'>This is a demonstration
585      collection for the Greenstone3 digital library software.</displayItem>
586    <displayItem name='icon' lang='en'>gs3mgdemo.gif</displayItem>
587    <displayItem name='smallicon' lang='en'>gs3mgdemo_sm.gif</displayItem>
588  </displayItemList>
589  <search>
590    <index name="ste">
591      <displayItem name='name' lang="en">chapters</displayItem>
592      <displayItem name='name' lang="fr">chapitres</displayItem>
593      <displayItem name='name' lang="es">capítulos</displayItem>
594    </index>
595    [ ... more indexes ...]
596    <format>
597      <gsf:template match="documentNode"><td valign='top'>
598       <gsf:link><gsf:icon/></gsf:link></td><td><gsf:metadata name='Title'/>
599      </td></gsf:template>
600    </format>
601  </search>
602  <browse>
603    <classifier name="CL1" horizontalAtTop='true'>
604      <displayItem name='name' lang='en'>Titles</displayItem>
605    </classifier>
606    [... more classifiers ...]
607    <classifier name="CL4">
608      <displayItem name='name' lang='en'>HowTo</displayItem>
609      <format>
610        <gsf:template match="documentNode">
611          <br /><gsf:link><gsf:metadata name='Keyword' />
612            </gsf:link></gsf:template>
613      </format>
614    </classifier>
615  </browse>
616  <display>
617    <format>
618      <gsf:option name="coverImages" value="false"/>
619      <gsf:option name="documentTOC" value="false"/>
620    </format>
621  </display>
622</collectionConfig>
623\end{verbatim}\end{gsc}
624\caption{Sample collectionConfig.xml file}
625\label{fig:collconfig}
626\end{figure}
627
628The \gst{<metadataList>} element specifies some collection metadata, such as creator. The \gst{<displayItemList>} specifies some language dependent information that is used for collection display, such as collection name and short description. These \gst{displayItem} elements can be specified in different languages.
629 
630The \gst{<search>} element provides some display and formatting information for the search indexes, while the \gst{<browse>} element concerns classifiers, and   the \gst{<display>} element looks at document display.
631
632Inside the \gst{<search>} and \gst{<browse>} elements, \gst{<displayItem>} elements are used to provide titles for the indexes or classifiers, while \gst{<format>} elements provide formatting instructions, typically for a document or classifier node in a list of results. Placing the \gst{<format>} instructions at the top level in the \gst{search} or \gst{browse} element will apply the format to all the indexes or classifiers, while placing it inside an individual \gst{index} or \gst{classifier} element will restrict that formatting instruction to that item.
633
634The \gst{<display>} element contains optional formatting information for the display of documents. Templates that can be specified here include \gst{documentHeading} and \gst{DocumentContent}. Other formatting options may also be specified here, such as whether to display a table of contents and/or cover image for the documents.
635
636Format elements are described in Section~\ref{sec:formatstmt}.
637
638An optional \gst{<replaceList>} element can be included at the top level. This contains a list of strings and their replacements. This is particularly useful for \gsii\  collections that use macros.
639
640The format is like the following:
641\begin{gsc}\begin{verbatim}
642<replaceList>
643<replace scope='text' macro="xxx" text="yyy"/>
644<replace scope='metadata' macro="xxx" bundle="yyy" key="zzz"/>
645<replace scope='all' macro='xxx' metadata='yyy'/>
646</replaceList>
647\end{verbatim}\end{gsc}
648
649Scope determines on what text the replacements are carried out: \gst{text}, \gst{metadata}, and \gst{all} (both text and metadata). An empty scope attribute is equivalent to scope=all. Each replace type can be used with all scope values. Replacing uses Java's 'String.replaceAll' functionality, so macro and replacement text are actually regular expressions. The first example is a straight textual replacement. The second example uses dictionary lookups. xxx will be replaced with the (language-dependent) value for key zzz in resource bundle yyy. The third example uses metadata: xxx will be replaced by the value of the yyy metadata for that document.
650
651Appendix~\ref{app:gs2replace} gives some examples that have been used for \gsii\  collections.
652
653\subsubsection{buildConfig.xml}\label{sec:buildconfig}
654
655The file \gst{buildConfig.xml} is produced by the collection building process. Generally it is not necessary to look at this file, but it can be useful in determining what went wrong if the collection doesn't appear quite the way it was planned.
656
657It contains metadata and other information about the collection that can
658be determined automatically, such as the number of
659documents in the collection.  It also includes a list of \gst{ServiceRack} classes that are
660required to provide the services that have been built into the
661collection.  The serviceRack names are Java classes that are loaded
662dynamically at runtime. Any information inside the serviceRack element is
663specific to that service---there is no set format. Figure~\ref{fig:buildconfig} shows an example. This configuration file specifies that the collection should load up 3 ServiceRacks: \gst{GS2Browse}, \gst{GS2MGPPRetrieve} and \gst{GS2MGPPSearch}. The contents of each \gst{<serviceRack>} element are passed to the appropriate ServiceRack objects for configuration. The \gst{collectionConfig.xml} file content is also passed to the ServiceRack objects at configure time---the \gst{format} and \gst{displayItem} information is used directly from the \gst{collectionConfig.xml} file rather than added into \gst{buildConfig.xml} during building. This enables formatting and metadata changes in \gst{collectionConfig.xml} to take effect in the collection without rebuilding being necessary. However, as these files are cached, the collection needs to be reloaded for the changes to appear in the library.
664
665
666\begin{figure}
667\begin{gsc}\begin{verbatim}
668<buildConfig>
669  <metadataList>
670    <metadata name="numDocs">11</metadata>
671    <metadata name="buildType">mgpp</metadata>
672  </metadataList>
673  <serviceRackList>
674    <serviceRack name="GS2Browse">
675      <indexStem name="gs2mgppdemo"/>
676      <classifierList>
677        <classifier name="CL1" content="Title"/>
678        <classifier name="CL2" content="Subject" />
679        <classifier name="CL3" content="Organization" />
680        <classifier name="CL4" content="Howto" />
681      </classifierList>
682    </serviceRack>
683    <serviceRack name="GS2MGPPRetrieve">
684      <indexStem name="gs2mgppdemo"/>
685      <defaultLevel name="Sec" />
686    </serviceRack>
687    <serviceRack name="GS2MGPPSearch">
688      <indexStem name="gs2mgppdemo"/>
689      <defaultLevel name="Sec" />
690      <levelList>
691        <level name="Sec" />
692        <level name="Doc" />
693      </levelList>
694      <fieldList>
695        <field shortname="ZZ" name="allfields" />
696        <field shortname="TX" name="text" />
697        <field shortname="DL" name="dls.Title" />
698        <field shortname="DS" name="dls.Subject" />
699        <field shortname="DO" name="dls.Organization" />
700      </fieldList>
701      <searchTypeList>
702        <searchType name="form" />
703        <searchType name="plain" />
704      </searchTypeList>
705      <indexOptionList>
706        <indexOption name="stemIndexes" value="3"/>
707    <indexOption name="maxnumeric" value="4"/>
708      </indexOptionList>
709      <defaultIndex name="idx" />
710      <indexList>
711        <index name="idx" />
712      </indexList>
713    </serviceRack>
714  </serviceRackList>
715</buildConfig>
716\end{verbatim}\end{gsc}
717\caption{Sample buildConfig.xml file (gs2mgppdemo collection)}
718\label{fig:buildconfig}
719\end{figure}
720
721\subsection{Formatting the collection}\label{sec:formatstmt}
722
723Part of collection design involves deciding how the collection should look. \gsiii\  has a default 'look' for a collection, so this is optional. However, the default may not suit the purposes of some collections, so many parts to the look of a collection can be determined by the collection designer.
724
725In standard \gsiii, the library is served to a web browser by a servlet, and the HTML is generated using XSLT. XSLT templates are used to format all the parts of the pages. These templates can be overridden by including them in the \gst{collectionConfig.xml} file. Some commonly overridden templates are those for formatting lists: search results list, classifier browsing hierarchies, and for parts of the document display.
726
727Real XSLT templates for formatting search results or classifier lists are quite complicated, and not at all easy for a new user to write. For example, the following is a sample template for formatting a classifier list, to show Keyword metadata as a link to the document.
728 
729\begin{gsc}\begin{verbatim}
730<xsl:template match="documentNode" priority="2"
731     xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
732  <xsl:param name="collName"/>
733    <td><a href="{$library_name}?a=d&amp;c={$collName}&amp;
734           d={@nodeID}&amp;dt={@docType}"><xsl:value-of
735           select="metadataList/metadata[@name='Keyword']"/></a>
736    </td>
737</xsl:template>
738 \end{verbatim}\end{gsc}
739 
740To write this, the user would need to know that:
741\begin{bulletedlist}
742\item the variable \gst{\$library\_name} exists,
743\item the collection name is passed in as a parameter called \gst{collName}
744\item metadata for a document is found in a \gst{<metadataList>} and that its form is \gst{<metadata name="Keyword">the value</metadata>}
745\item the arguments needed for the link to the document are \gst{a, sa, c, d, a, dt}.
746\end{bulletedlist}
747 
748We can use XSLT to transform XML into XSLT. \gsiii\  provides a simplified set of formatting commands, written in XML, which will be transformed into proper XSLT. The user specifies a \gst{<gsf:template>} for what they want to format---these typically match \gst{documentNode} or \gst{classifierNode} (for a node in a classification hierarchy).
749 
750The template above can be represented as:
751 
752\begin{gsc}\begin{verbatim}
753<gsf:template match='documentNode'>
754  <td><gsf:link><gsf:metadata name='Keyword'/></gsf:link></td>
755</gsf:template>
756\end{verbatim}\end{gsc}
757
758Table~\ref{tab:gsf-format} shows the set of \gst{'gsf'} (Greenstone Format) elements. If you have come from a \gsii\  background, Appendix~\ref{app:gs2format} shows \gsii\  format elements and their equivalents in \gsiii\ .
759 
760\begin{table}
761\caption{Format elements for GSF format language}
762\label{tab:gsf-format}
763{\footnotesize
764\begin{tabular}{p{6.5cm}p{6.5cm}}
765\hline
766\bf Element       & \bf Description \\
767\hline
768\gst{<gsf:text/>} & The document's text\\
769\hline
770\gst{<gsf:link>...</gsf:link>} & The HTML link to the document itself \\
771\gst{<gsf:link type='document'>...
772</gsf:link>} & Same as above\\
773\gst{<gsf:link type='classifier'>...
774</gsf:link>} & A link to a classification node (use in classifierNode templates)\\
775\gst{<gsf:link type='source'>...
776</gsf:link>} & The HTML link to the original file---set for documents that have been converted from e.g. Word, PDF, PS \\
777\hline
778\gst{<gsf:icon/>}  & An appropriate icon\\
779\gst{<gsf:icon type='document'/>} & same as above\\
780\gst{<gsf:icon type='classifier'/>} & bookshelf icon for classification nodes\\
781\gst{<gsf:icon type='source'/>} & An appropriate icon for the original file e.g. Word, PDF icon\\
782\hline
783\gst{<gsf:metadata name='Title'/>} & The value of a metadata element for the current document or section, in this case, Title\\
784\gst{<gsf:metadata name='Title' select='select-type' [separator='y' multiple='true']/>} & A more extended selection of metadata values. The select field can be one of those shown in Table~\ref{tab:gsf-select-types}. There are two optional attributes: separator gives a String that will be used to separate the fields, default is ``, ``, and if multiple is set to true, looks for multiple values at each section.\\
785\gst{<gsf:metadata name='Date' format='formatDate'/>} & The value of a metadata element for the current document, formatted in some way. Current formatting options available are formatDate: turns '20040201' into '01 February 2004', and formatLanguage: turns 'en' into 'English', both in a language dependent manner. \\
786\hline
787\gst{<gsf:choose-metadata>
788  <gsf:metadata name='metaA'/>
789  <gsf:metadata name='metaB'/>
790  <gsf:metadata name='metaC'/>
791</gsf:choose-metadata>}
792 & A choice of metadata. Will select the first existing one. the metadata elements can have the select, separator and multiple attributes like normal.\\
793\hline
794\gst{<gsf:switch preprocess=
795'preprocess-type'>
796<gsf:metadata name='Title'/> 
797<gsf:when test='test-type'
798test-value='xxx'>...</gsf:when>
799<gsf:when test='test-type'
800test-value='yyy'>...</gsf:when>
801<gsf:otherwise>...</gsf:otherwise>
802</gsf:switch>} & switch on the value of a particular metadata - the metadata is specified in gsf:metadata, has the same attributes as normal.\\
803\hline
804\end{tabular}}
805\end{table}
806
807The \gst{<gsf:metadata>} elements are used to output metadata values. The simplest case is \gst{<gsf:metadata name='Title'/>}---this outputs the Title metadata for the current document or section. Namespaces are important here: if the Title metadata is in the Dublin Core (dc) namespace, then the element should look like \gst{<gsf:metadata name='dc.Title'/>}. There are three other attributes for this element. The attribute \gst{multiple} is used when there may be more than one value for the selected metadata.
808For instance, one document may fall into several classification categories, and therefore may have multiple Subject metadata values. Adding \gst{multiple='true'} to the \gst{<gsf:metadata>} element will retrieve all values, not just the first one. Multiple values are separated by commas by default. The \gst{separator} attribute is used to change the separating string. For example, adding \gst{separator=':~'} to the element will separate all values by a colon and a space.
809
810Sometimes you may want to display metadata values for sections other than the current one. For example, in the mgppdemo collection, in a search list we display the Titles of all the enclosing sections, followed by the Title of the current section, all separated by semi-colons. The display ends up looking something like:
811\emph{Farming snails 2; Starting out; Selecting your snails}
812where \emph{Selecting your snails} is the Title of the section in the results list, and \emph{Farming snails 2} and \emph{Starting out} are the Titles of the enclosing sections. The \gst{select} attribute is used to display metadata for sections other than the current one. Table~\ref{tab:gsf-select-types} shows the options available for this attribute. The \gst{separator} attribute is used here also, to specify the separating text.
813
814To get the previous metadata, the format statement would have the following in it:
815
816\begin{gsc}
817\begin{verbatim}
818<gsf:metadata name='Title' select='ancestors' separator='; '/>;
819    <gsf:metadata name='Title'/>
820\end{verbatim}
821\end{gsc}
822
823\begin{table}
824\caption{Select types for metadata format elements}
825\label{tab:gsf-select-types}
826{\footnotesize
827\begin{tabular}{ll}
828\hline
829\bf Select Type & \bf Description\\
830\hline
831current & The current section \\
832parent & The immediate parent section\\
833ancestors & All the parents back to the root (topmost) section\\
834root & The root or topmost section \\
835siblings & All the sibling sections\\
836children & The immediate child sections of the current section\\
837descendants & All the descendent sections\\
838\hline
839\end{tabular}}
840\end{table}
841
842The \gst{<gsf:choose-metadata>} element selects the first available metadata value from the list of options.
843\begin{gsc}
844\begin{verbatim}
845<gsf:choose-metadata>
846  <gsf:metadata name='dc.Title'/>
847  <gsf:metadata name='dls.Title'/>
848  <gsf:metadata name='Title'/>
849</gsf:choose-metadata>
850\end{verbatim}
851\end{gsc}
852
853This will display dls.Title if available, otherwise it will use dc.Title if available, otherwise it will use the Title metadata. If there are no values for any of these metadata elements, then nothing will be displayed.
854
855The \gst{<gsf:switch>} element allows different formatting depending on the value of a specified metadata element. For example, the following switch statement could be used to display a different icon for each document in a list depending on which organization it came from.
856
857\begin{gsc}
858\begin{verbatim}
859<gsf:switch  preprocess='toLower;stripSpace'>
860  <gsf:metadata name='Organization'/>
861  <gsf:when test='equals' test-value='bostid'>
862     <!-- output BOSTID image --></gsf:when>
863  <gsf:when test='equals' test-value='worldbank'>
864     <!-- output world bank image --></gsf:when>
865  <gsf:otherwise><!-- output default image--></gsf:otherwise>
866</gsf:switch>
867\end{verbatim}
868\end{gsc}
869
870Preprocessing of the metadata value is optional. The preprocess types are \gst{toLower} (make the value lowercase), \gst{toUpper} (make the value uppercase), \gst{stripSpace} (removes any whitespace from the value). These operations are carried out on the value of the selected metadata before the test is carried out. Multiple processing types can be specified, separated by ; and they will be applied in the order specified (from left to right).
871
872Each option specifies a test and a test value. Test values are just text. Tests include \gst{startsWith}, \gst{contains}, \gst{exists}, \gst{equals}, \gst{endsWith}. Exists doesn't need a test value. Having an otherwise option ensures that something will be displayed even when none of the tests match.
873
874If none of the gsf elements meets your needs for formatting, XSLT can be entered directly into the format element, giving the collection designer full flexibility over how the collection appears.
875
876The collection specific templates are added into the configuration file \gst{collectionConfig.xml}. Any templates found in the XSLT files can be overridden.
877The important part to adding templates into the configuration file is determining where to put them. Formatting templates cannot go just anywhere---there are standard places for them. Figure~\ref{fig:format-places} shows the positions that templates can occur.
878
879\begin{figure}
880\begin{gsc}\begin{verbatim}
881<collectionConfig>
882  <metadataList/>
883  <displayItemList/>
884  <search>
885    <format> <!--Put here templates related to searching and
886        the query page. The common one is the documentNode
887        template -->
888      <gsf:template match='documentNode'>...</gsf:template>
889    </format>
890  </search>
891  <browse>
892    <classifier name='xx'>
893      <format><!-- put here templates related to formating a
894        particular classifier page. Common ones are documentNode
895        and classifierNode templates-->
896        <gsf:template match='documentNode'>...</gsf:template>
897        <gsf:template match='classifierNode'>...</gsf:template>
898        <gsf:template match='classifierNode' mode='horizontal'>...
899          </gsf:template>
900      </format>
901    </classifier>
902    <classifier>...</classifier>
903    <format><!-- formatting for all the classifiers. these will
904      be overridden by any classifier specific formatting
905      instructions --></format>
906  </browse>
907  <display>
908    <format><!-- here goes any formatting relating to the display
909        of the documents. These are generally named templates,
910        and format options -->
911      <gsf:template name='documentContent'>...</gsf:template>
912      <gsf:option name='TOC' value='true'/>
913    </format>
914  </display>
915</collectionConfig>
916\end{verbatim}\end{gsc}
917\caption{Places for format statements}
918\label{fig:format-places}
919\end{figure}
920
921 
922There are also formatting instructions that are not templates but are options.
923These are described in Table~\ref{tab:format_options}. They are entered into the configuration file like \gst{<gsf:option name='coverImages' value='false'/>}
924
925\begin{table}
926\caption{Formatting options}
927\label{tab:format_options}
928{\footnotesize
929\begin{tabular}{llp{5cm}}
930\hline
931\bf option name & \bf values & \bf description \\
932\hline
933coverImages & true, false & whether or not to display cover images for documents \\
934documentTOC & true, false & whether or not to display the table of contents for the document\\
935\hline
936\end{tabular}}
937\end{table}
938
939Note, format templates are added into the XSLT files before transforming, while the options are added into the page source, and used in tests in the XSLT.
940
941\subsubsection{Changing the service text strings}
942
943Each collection has a set of services which are the access points for the information in the collection. Each service has a set of text strings which are used to display it. These include name, description, the text on the submit button, and names and descriptions of all the parameters to the service.
944
945These text strings are found in \gst{.properties} files, in \gst{\$GSDL3HOME/WEB-INF/classes}. The names of the files are based on class names. Subclasses can define their own properties, or can use their parent class ones. For example, \gst{AbstractSearch} defines strings for the \gst{TextQuery} service, in \gst{AbstractSearch.properties}. \gst{GS2MGSearch} just uses these default ones, so doesn't need its own properties file.
946
947A particular collection can override the properties for any service. For example, if a collection uses the \gst{GS2MGSearch} service rack (look in the \gst{buildConfig.xml} file for a list of service racks used), and the collection builder wants to change the text associated with this service, they can put a \gst{GS2MGSearch.properties} file in the resources directory of the collection. After a reconfigure of the collection, this will be used in preference to the one in the default resources directory.
948
949\subsection{Customizing the interface}\label{sec:interface-customise}
950
951Format statements in the collection configuration files provide a way to change small parts of the collection display. For large scale customizations to a collection, or ones that apply to a site as a whole, a second mechanism is available. The interface is defined by a set of XSLT files that transform the page data into HTML. Any of these files can be overridden to provide specialized display, on a site or collection basis.
952
953The first section looks at customizing the existing interface, while the second section looks at defining a whole new interface. The last section describes how to add a new language translation of an interface.
954
955\subsubsection{Modifying an existing interface}
956
957Most of an interface is defined by XSLT files, which are stored in \gst{\$GSDL3HOME/\-interfaces/\-interface-name/\-transform}. These can be changed and the changes will take effect straight away. If changes only apply to certain collections or sites, not everything that uses the interface, you can override some of the files by putting new ones in a different place. XSLT files are looked for in the following  order: collection, site, interface, default interface. (This currently only apples to sites, and therefore collections, that reside in the same \gs\  installation as the interface.)
958
959Sites and collections can have a transform directory, which is where customized XSLT files should go. Any XSLT files in here will be used in preference to the interface files when using this collection. For example, if you want to have a completely different layout for the about page of a collection, you can put a new \gst{about.xsl} file into the collection's \gst{transform} directory, and this will be used instead. This is what we do for the Gutenberg sample collection.
960
961This also applies to files that are included from other XSLT files. For example the \gst{query.xsl} for the query pages includes a file called \gst{querytools.xsl}. To have a particular site show a different query interface either of these files may need to be modified. Creating a new version of either of these and putting it in the site \gst{transform} directory will work. Either the new \gst{query.xsl} will include the default \gst{querytools.xsl}, or the default \gst{query.xsl} will include the new \gst{querytools.xsl}. The \gst{xsl:include} directives are preprocessed by the Java code and full paths added based on availability of the files, so that the correct one is used.
962
963Note that you cannot include a file with the same name as the including file. For example \gst{query.xsl} cannot include \gst{query.xsl} (it is tempting to want to do this if you just want to change one template for a particular file, and then include the default. but you cant).
964
965You can add the argument \gst{o=xml} to any URL and you wil be returned the XML before transformation by a stylesheet. This shows you the XML page source. It can be useful when you are trying to write some new XSLT statements.
966
967\subsubsection{Defining a new interface}
968
969A new interface may be needed if different instantiations of the library require different interfaces, or different developers want their own look and feel. Creating a new interface will allow modifications to be made while leaving the original one intact.
970
971A new interface needs a directory in \gst{\$GSDL3HOME/interfaces}, the name of this directory becomes the interface name. Inside, it needs \gst{images} and \gst{transform} directories,  and an \gst{interfaceConfig.xml} file. The \gst{interfaceConfig.xml} file may specify a base interface, in which case the new interface only needs to define XSLT for the parts that are different. Otherwise, it will need a full set of XSLT files.
972
973To use a new interface, the \gst{\$GSDL3HOME/WEB-INF/web.xml} file must be edited: either change the interface that a current servlet instance is using, or add another servlet instantiation to the file (see Section~\ref{sec:sites-and-ints} or Appendix~\ref{app:tomcat}). The Tomcat server must be restarted for this to take effect.
974
975\subsubsection{Changing the interface language}\label{sec:interface-language}
976
977The interface language can be changed by going to the preferences page, and choosing a language from the list, which includes all languages into which the interface has been translated.
978
979It is easy to add a new interface language to \gs\ .  Language specific text strings are separated out from the rest of the system to allow for easy incorporation of new languages. These text strings are contained in Java resource bundle properties files. These are plain text files consisting of key-value pairs, located in \gst{\$GSDL3HOME/WEB-INF/classes}. Each interface has one named \gst{interface\_name.properties} (where \gst{'name'} is the interface name, for example, \gst{interface\_default.properties}, or \gst{interface\_gs2.properties}). Each service class has one with the same name as the class (e.g. \gst{GS2Search.properties}). To add another language all of the base \gst{.properties}  files must be translated. The translated files keep the same names, but with a language extension added. For example, a French version of \gst{interface\_default.properties} would be named \gst{interface\_default\_fr.properties}.
980
981Keys will be looked up in the properties file closest to the specified language. For example, if language \gst{fr\_CA} was specified (French language, country Canada), and the default locale was \gst{en\_GB},  Java would look at properties files in the following order, until it found the key: \gst{XXX\_fr\_CA.properties}, \gst{XXX\_fr.properties},  \gst{XXX\_en\_GB.properties}, then \gst{XXX\_en.properties}, and finally the default \gst{XXX.properties}.
982
983These new files are available straight away---to use the new language, add e.g. \gst{l=fr} to the arguments in the URL. To get \gs\ to add it in to the list of languages on the preferences page, an entry needs to be added into the languages list in the \gst{interfaceConfig.xml} file (see Section~\ref{sec:interfaceconfig}). Modification of this file requires a restart of the Tomcat server for the changes to be recognized.
984
985\newpage
986\section{Developing \gsiii : Run-time system}\label{sec:develop-runtime}
987
988[TODO: rewrite this section\\
989runtime object structure diagram. describe the modules.\\
990class hierarchy,\\
991directory structure and where everything lives\\
992message format.\\
993overall description of message passing sequence.\\
994configuration process - start up and runtime\\
995\\
996page generation\\
997]
998\subsection{Overview of modules??}
999
1000A \gsiii\  'library' system consists of many components: MessageRouter, Receptionist, Actions, Collections, ServiceRacks etc.  Figure~\ref{fig:local} shows how they fit together in a stand-alone system. The top left part is concerned with displaying the data, while the bottom right part is the collection data serving part. The two sides communicate through the MessageRouter. There is a one-to-one correspondence between modules and Java classes, with the exception of services: for coding and/or run-time efficiency reasons, several Service modules may be grouped together into one ServiceRack class.
1001
1002\begin{figure}[t]
1003  \centering
1004  \includegraphics[width=4in]{local} %5.8
1005  \caption{A simple stand-alone site.}
1006  \label{fig:local}
1007\end{figure}
1008
1009
1010{\em MessageRouter}: this is the central module for a site. It controls the site, loading up all the collections, clusters, communicators needed. All messages pass through the MessageRouter. Communication between remote sites is always done between MessageRouters, one for each site.
1011
1012{\em Collection and ServiceCluster}: these are very similar, and group a set of services into a conceptual group.. They both provide some metadata about the collection/cluster, and a list of services. The services are provided by ServiceRack objects that the collection/cluster loads up. A Collection is a specific type of ServiceCluster. A ServiceCluster groups services that are related conceptually, e.g. all the building services may be part of a cluster. What is part of a cluster is specified by the site configuration file. A Collection's services are grouped by the fact that they all operate on some common data---the documents in the collection.
1013Functionally Collection and ServiceCluster are very similar, but conceptually, and to the user, they are quite different.
1014
1015{\em Service}: these provide the core functionality of the system e.g. searching, retrieving documents, building collections etc. One or more may be grouped into a single Java class (ServiceRack) for code reuse, or to avoid instantiating the same objects several times. For example, MGPP searching services all need to have the index loaded into memory.
1016
1017{\em Communicator/Server}: these facilitate communication between remote modules. For example, if you want MR1 to talk to MR2, you need a Communicator-Server pair. The Server sits on top of MR2, and MR1 talks to the Communicator. Each communication type needs a new pair. So far we have only been using SOAP, so we have a SOAPCommunicator and a SOAPServer.
1018
1019{\em Receptionist}: this is the point of contact for the 'front end'. Its core functionality involves routing requests to the Actions, but it may do more than that. For example, a Receptionist may: modify the request in some way before sending it to the appropriate Action; add some data to the page responses that is common to all pages; transform the response into another form using XSLT. There is a hierarchy of different Receptionist types, which is described in Section~\ref{sec:recepts}.
1020
1021{\em Actions}: these do the job of creating the 'pages'. There is a different action for each type of page, for example PageAction handles semi-static pages, QueryAction handles queries, DocumentAction displays documents. They know a little bit about specific service types. Based on the 'CGI' arguments passed in to them, they construct requests for the system, and put together the responses into data for the page. This data is returned to the Receptionist, which may transform it to HTML. The various actions are described in  more detail in Section~\ref{sec:pagegen}.
1022
1023
1024\subsection{Start up configuration}\label{sec:startup-config}
1025
1026We use the Tomcat web server, which operates either stand-alone in a test mode
1027or in conjunction with the Apache web server.  The \gs\  LibraryServlet
1028class is loaded by Tomcat  and the servlet's \gst{init()} method is called.  Each time a
1029\gst{get/put/post} (etc.) is used, a new thread is started and
1030\gst{doGet()/doPut()/doPost()} (etc.) is called.
1031
1032The \gst{init()} method creates a new Receptionist and a new
1033MessageRouter. Default classes (DefaultReceptionist, MessageRouter) are used unless subclasses have been specified  in the servlet initiation parameters (see Section~\ref{sec:sites-and-ints}). The appropriate system variables are set for each object (interface
1034name, site name, etc.) and then \gst{configure()} is called on both. The MessageRouter handle
1035is passed to the Receptionist. The servlet then communicates only with
1036the Receptionist, not with the MessageRouter.
1037
1038The Receptionist reads in the \gst{interfaceConfig.xml} file (see Section~\ref{sec:interfaceconfig}), and loads up all the different Action classes. Other Actions may be loaded on the fly as needed. Actions are added to a map, with shortnames for keys. Eg the QueryAction is added with key 'q'. The Actions are passed the MessageRouter reference too.
1039If the Receptionist is a TransformingReceptionist, a mapping between shortnames  and XSLT file names is also created.
1040
1041The MessageRouter reads in its site configuration file \gst{siteConfig.xml} (see Section~\ref{sec:siteconfig}). It creates a module map that maps names to objects. This is used for routing the messages. It also keeps small chunks of XML---serviceList, collectionList, clusterList and siteList. These are part of what get returned in response to a describe request (see Section~\ref{sec:describe}.).
1042
1043Each ServiceRack specified in the configuration file is created, then queried for its list of services. Each service name is added to the map, pointing to the ServiceRack object. Each service is also added to the serviceList. After this stage, ServiceRacks are transparent to the system, and each service is treated as a separate module.
1044
1045ServiceClusters are created and passed the \gst{<serviceCluster>} element for configuration. They are added to the map as is, with the cluster name as a key. A serviceCluster is also added to the serviceClusterList.
1046
1047For each site specified, the MessageRouter creates an appropriate type of Communicator object. Then it tries to get the site description. If the server for the remote site is up and running, this should  be successful. The site will be added to the mapping with its site name as a key. The site's collections, services and clusters will also be added into the static xml lists. If the server for the remote site is not running, the site will not be included in the siteList or module map. To try again to access the site, either Tomcat must be restarted, or a run-time reconfigure-site command must be sent (see Section~\ref{sec:runtime-config}).
1048
1049The MessageRouter also looks inside the site's \gst{collect} directory, and  loads up a Collection object for each valid collection found. If a \gst{collectionInit.xml} file is present, a subclass of Collection may be used.
1050The Collection object reads its \gst{buildConfig.xml} and \gst{collectionConfig.xml}
1051files, determines the metadata, and loads ServiceRack classes based on the
1052names specified in \gst{buildConfig.xml\/}. The \gst{<serviceRack>} XML element is passed to the object to be used in configuration. The \gst{collectionConfig.xml} contents are also passed in to the ServiceRacks. Any format or display information that the services need must be extracted from the collection configuration file.
1053Collection objects are added to the module map with their name as a key, and also a collection element is added into the collectionList XML.
1054
1055\subsection{Message passing}
1056
1057There are two types of messages used by the system: external and internal messages. All messages have an enclosing \gst{<message>} element, which contains either one or more requests, or one or more responses. In the following descriptions, the message element is not shown, but is assumed to be present. 
1058Action in \gsiii\  is originated by a request coming in from the outside. In the standard web-based \gs, this comes from a servlet and is passed into the Receptionist. This ``external'' type request is a request for a page of data, and contains a representation of the CGI style arguments. A page of XML is returned, which can be in HTML format or other depending on the output parameter of the request.
1059
1060Messages inside the system (``internal'' messages) all follow the same basic format: message elements contain multiple request elements, or multiple response elements. Messaging is all synchronous. The same number of responses as requests will be returned. Currently all requests are independent, so any requests can be combined into the same message, and they will be answered separately, with their responses being sent back in a single message.
1061
1062When a page request (external request) comes in to the Receptionist, it looks at the action attribute and passes the request to the appropriate Action module. The Action will fire one or more internal requests to the MessageRouter, based on the arguments. The data is gathered into a  response, which is returned to the Receptionist.  The page that the receptionist returns contains the original request, the response from the action and other info as needed (depends on the type of Receptionist). The data may be transformed in some way --- for the \gs\ servlet  we transform using XSLT to generate HTML pages.
1063
1064Actions send internal style messages to the MessageRouter. Some can be answered by it, others are passed on to collections, and maybe on to services. Internal requests are for simple actions, such as search, retrieve metadata, retrieve document text
1065There are different internal request types: describe, process, system, format, status. Process requests do the actual work of the system, while the other types get auxiliary information. The format of the requests and responses for each internal request type are described in the following sections. External style requests, and their page responses are described in the Section about page generation (Section~\ref{sec:pagegen}).
1066
1067\subsection{'describe'-type messages}\label{sec:describe}
1068
1069The most basic of the internal standard requests is ``describe-yourself'', which can be sent to any module in the system. The module responds with a semi-predefined piece of XML, making these requests very efficient. The response is predefined apart from any language-specific text strings, which are put together as each request comes in, based on the language attribute of the request.
1070\begin{quote}\begin{gsc}\begin{verbatim}
1071<request lang='en' type='describe' to=''/>
1072\end{verbatim}\end{gsc}\end{quote}
1073If the \gst{to} field is empty, a request is answered by the MessageRouter.
1074An example response from a MessageRouter might look like this:
1075\begin{quote}\begin{gsc}\begin{verbatim}
1076<response lang='en' type='describe'>
1077  <serviceList/>
1078  <siteList>
1079    <site name='org.greenstone.gsdl1'
1080            address='http://localhost:8080/greenstone3/services/localsite'
1081            type='soap' />
1082  </siteList>
1083  <serviceClusterList>
1084    <serviceCluster name="build" />
1085  </serviceClusterList>
1086  <collectionList>
1087    <collection name='org.greenstone.gsdl1/
1088                  org.greenstone.gsdl2/fao' />
1089    <collection name='org.greenstone.gsdl1/demo' />
1090    <collection name='org.greenstone.gsdl1/fao' />
1091    <collection name='myfiles' />
1092  </collectionList>
1093</response>
1094\end{verbatim}\end{gsc}\end{quote}
1095This MessageRouter has no individual site-wide services (an empty \gst{<serviceList>}), but has a service cluster called build (which provides collection importing and building functionality).  It
1096communicates with one site, \gst{org.greenstone.gsdl1}.  It is aware of four
1097collections.  One of these, \gst{myfiles}, belongs to it; the other three are
1098available through the external site.  One of those collections is actually from
1099a further external site.
1100
1101It is possible to ask just for a specific part of the information provided by a
1102describe request, rather than the whole thing. For example, these two
1103messages get the \gst{collectionList} and the \gst{siteList} respectively:
1104\begin{quote}\begin{gsc}\begin{verbatim}
1105<request lang='en' type='describe' to=''>
1106  <paramList>
1107    <param name='subset' value='collectionList'/>
1108  </paramList>
1109</request>
1110
1111<request lang='en' type='describe' to=''>
1112  <paramList>
1113    <param name='subset' value='siteList'/>
1114  </paramList>
1115</request>
1116\end{verbatim}\end{gsc}\end{quote}
1117
1118Subset options for the MessageRouter include \gst{collectionList}, \gst{serviceClusterList}, \gst{serviceList}, \gst{siteList}.
1119
1120When a collection or service cluster is asked to describe itself, what is returned is a list of metadata, some display elements, and  a list of services.  For example, here is such a message, along with a sample response.
1121
1122\begin{quote}\begin{gsc}\begin{verbatim}
1123<request lang='en' type='describe' to='mgppdemo'/>
1124
1125<response from="mgppdemo" type="describe">
1126  <collection name="mgppdemo">
1127    <displayItem lang="en" name="name">greenstone mgpp demo
1128    </displayItem>
1129    <displayItem lang="en" name="description">This is a
1130      demonstration collection for the Greenstone digital
1131      library software. It contains a small subset (11 books)
1132      of the Humanity Development Library. It is built with
1133      mgpp.</displayItem>
1134    <displayItem lang="en" name="icon">mgppdemo.gif</displayItem>
1135    <serviceList>
1136      <service name="DocumentStructureRetrieve" type="retrieve" />
1137      <service name="DocumentMetadataRetrieve" type="retrieve" />
1138      <service name="DocumentContentRetrieve" type="retrieve" />
1139      <service name="ClassifierBrowse" type="browse" />
1140      <service name="ClassifierBrowseMetadataRetrieve"
1141            type="retrieve" />
1142      <service name="TextQuery" type="query" />
1143      <service name="FieldQuery" type="query" />
1144      <service name="AdvancedFieldQuery" type="query" />
1145      <service name="PhindApplet" type="applet" />
1146    </serviceList>
1147    <metadataList>
1148      <metadata name="creator">greenstone@cs.waikato.ac.nz</metadata>
1149      <metadata name="numDocs">11</metadata> 
1150      <metadata name="buildType">mgpp</metadata>
1151      <metadata name="httpPath">http://kanuka:8090/greenstone3/sites/
1152                                localsite/collect/mgppdemo</metadata>
1153    </metadataList>
1154  </collection>
1155</response>
1156\end{verbatim}\end{gsc}\end{quote}
1157
1158Subset options for a collection or serviceCluster include \gst{metadataList}, \gst{serviceList}, and \gst{displayItemList}.
1159
1160This collection provides many typical services. Notice how this response lists the services available, while the collection configuration file for this collection (Figure~\ref{fig:collconfig}) described serviceRacks. Once the service racks have been configured, they become transparent in the system, and only services are referred to.
1161There are three document retrieval services, for structural information, metadata, and content. The Classifier services retrieve classification structure and metadata. These five services were all provided by the GS2MGPPRetrieve ServiceRack. The three query services were provided by GS2MGPPSearch serviceRack, and provide different kinds of query interface. The last service, PhindApplet, is provided by the PhindPhraseBrowse serviceRack and is an applet service.
1162
1163A \gst{describe} request sent to a service returns a list of parameters that
1164the service accepts and some display information, (and in future may describe the content type for the request and response). Subset options for the request include \gst{paramList} and \gst{displayItemList}.
1165
1166Parameters can be in the following formats:
1167\begin{quote}\begin{gsc}\begin{verbatim}
1168<param name='xxx' type='integer|boolean|string|invisible' default='yyy'/>
1169<param name='xxx' type='enum_single|enum_multi' default='aa'/>
1170  <option name='aa'/><option name='bb'/>...
1171</param>
1172<param name='xxx' type='multi' occurs='4'>
1173 <param .../>
1174 <param .../>
1175</param>
1176\end{verbatim}\end{gsc}\end{quote}
1177
1178If no default is specified, the parameter is assumed to be mandatory.
1179Here are some examples of parameters:
1180\begin{quote}\begin{gsc}\begin{verbatim}
1181<param name='case' type='boolean' default='0'/>
1182
1183<param name='maxDocs' type='integer' default='50'/>
1184
1185<param name='index' type='enum' default='dtx'>
1186  <option name='dtx'/>
1187  <option name='stt'/>
1188  <option name='stx'/>
1189<param>
1190
1191<!-- this one is for the text box and field list for the
1192simple field query-->
1193<param name='simpleField' type='multi' occurs='4'>
1194  <param name='fqv' type='string'/>
1195  <param name='fqf' type='enum_single'>
1196    <option name='TI'/><option name='AU'/><option name='OR'/>
1197  </param>
1198</param>
1199
1200\end{verbatim}\end{gsc}\end{quote}
1201The type attribute is used to determine how to display the parameters on a web page or interface. For example, a string parameter may result in a text entry box, a boolean an on/off button, enum\_single/enum\_multi a drop-down menu, where one or many items, respectively, can be selected.
1202A multi-type parameter indicates that two or more parameters are associated, and should be displayed appropriately. For example, in a field query, the text box and field list should be associated. The occurs attribute specifies how many times the parameter should be displayed on the page.
1203Parameters also come with display information: all the text strings needed to present them to the user. These include the name of the parameter and the display values for any options. These are included in the above parameter descriptions in the form of \gst{<displayItem>} elements.
1204
1205A service description also contains some display information---this includes the name of the service, and the text  for the submit button.
1206
1207Here is a sample describe request to the FieldQuery service of collection mgppdemo, along with its response. The parameters in this example include their display information. Figure~\ref{fig:query-display} shows an example HTML search form that may be generated from this describe response.
1208
1209\begin{quote}\begin{gsc}\begin{verbatim}
1210<request lang="en" to="mgppdemo/FieldQuery" type="describe" />
1211
1212<response from="mgppdemo/FieldQuery" type="describe">
1213  <service name="FieldQuery" type="query">
1214    <displayItem name="name">Form Query</displayItem>
1215    <displayItem name="submit">Search</displayItem>
1216    <paramList>
1217      <param default="Doc" name="level" type="enum_single">
1218        <displayItem name="name">Granularity to search at</displayItem>
1219        <option name="Doc">
1220          <displayItem name="name">Document</displayItem>
1221        </option>
1222        <option name="Sec">
1223          <displayItem name="name">Section</displayItem>
1224        </option>
1225        <option name="Para">
1226          <displayItem name="name">Paragraph</displayItem>
1227        </option>
1228      </param>
1229      <param default="1" name="case" type="boolean">
1230        <displayItem name="name">Turn casefolding </displayItem>
1231        <option name="0">
1232          <displayItem name="name">off</displayItem>
1233        </option>
1234        <option name="1">
1235          <displayItem name="name">on</displayItem>
1236        </option>
1237      </param>
1238      <param default="1" name="stem" type="boolean">
1239        <displayItem name="name">Turn stemming </displayItem>
1240        <option name="0">
1241          <displayItem name="name">off</displayItem>
1242        </option>
1243        <option name="1">
1244          <displayItem name="name">on</displayItem>
1245        </option>
1246      </param>
1247      <param default="10" name="maxDocs" type="integer">
1248        <displayItem name="name">Maximum documents to return
1249        </displayItem>
1250      </param>
1251      <param name="simpleField" occurs="4" type="multi">
1252        <displayItem name="name"></displayItem>
1253        <param name="fqv" type="string">
1254          <displayItem name="name">Word or phrase </displayItem>
1255        </param>
1256        <param default="ZZ" name="fqf" type="enum_single">
1257          <displayItem name="name">in field</displayItem>
1258          <option name="ZZ">
1259            <displayItem name="name">allfields</displayItem>
1260          </option>   
1261          <option name="TX">
1262            <displayItem name="name">text</displayItem>
1263          </option>
1264          <option name="TI">
1265            <displayItem name="name">Title</displayItem>
1266          </option>
1267          <option name="SU">
1268            <displayItem name="name">Subject</displayItem>
1269          </option>
1270          <option name="ORG">
1271            <displayItem name="name">Organization</displayItem>
1272          </option>
1273          <option name="SO">
1274            <displayItem name="name">Source</displayItem>
1275          </option>
1276        </param>
1277      </param>
1278    </paramList>
1279  </service>
1280</response>
1281\end{verbatim}\end{gsc}\end{quote}
1282
1283\begin{figure}[t]
1284  \centering
1285  \includegraphics[width=3.5in]{query2.ps}
1286  \caption{The previous query service describe response as displayed on the search page.}
1287  \label{fig:query-display}
1288\end{figure}
1289
1290A describe request to an applet type service returns the applet HTML element: this will be embedded into a web page to run the applet.
1291\begin{quote}\begin{gsc}\begin{verbatim}
1292<request type='describe' to='mgppdemo/PhindApplet'/>
1293
1294<response type='describe'>
1295  <service name='PhindApplet' type='query'>
1296    <applet ARCHIVE='phind.jar, xercesImpl.jar, gsdl3.jar,
1297            jaxp.jar, xml-apis.jar'
1298            CODE='org.greenstone.applet.phind.Phind.class'
1299            CODEBASE='lib/java'
1300            HEIGHT='400' WIDTH='500'>
1301      <PARAM NAME='library' VALUE=''/>
1302      <PARAM NAME='phindcgi' VALUE='?a=a&amp;sa=r&amp;sn=Phind'/>
1303      <PARAM NAME='collection' VALUE='mgppdemo' />
1304      <PARAM NAME='classifier' VALUE='1' />
1305      <PARAM NAME='orientation' VALUE='vertical' />
1306      <PARAM NAME='depth' VALUE='2' />
1307      <PARAM NAME='resultorder' VALUE='L,l,E,e,D,d' />
1308      <PARAM NAME='backdrop' VALUE='interfaces/default/>
1309                      images/phindbg1.jpg'/>
1310      <PARAM NAME='fontsize' VALUE='10' />
1311      <PARAM NAME='blocksize' VALUE='10' />
1312      The Phind java applet.
1313    </applet>
1314    <displayItem name="name">Browse phrase hierarchies</displayItem>
1315  </service>
1316</response>
1317\end{verbatim}\end{gsc}\end{quote}
1318
1319Note that the library parameter has been left blank. This is because library refers to the current servlet that is running and the name is not necessarily known in advance. So either the applet action or the Receptionist must fill in this parameter before displaying the HTML.
1320
1321\subsection{'system'-type messages}\label{sec:system}
1322
1323``System'' requests are used to tell a MessageRouter, Collection or ServiceCluster to update its cached information and activate or deactivate other modules. For example, the MessageRouter has a set of Collection modules that it can talk to. It also holds some XML information about those collections---this is returned when a request for a collection list comes in. If a collection is deleted or modified, or a new one created, this information may need to change, and the list of available modules may also change. Currently these requests are initiated by particular CGI requests (see Section~\ref{sec:runtime-config}).
1324
1325The basic format of a system request is as follows:
1326
1327\begin{quote}\begin{gsc}\begin{verbatim}
1328<request type='system' to=''>
1329  <system .../>
1330</request>
1331\end{verbatim}\end{gsc}\end{quote}
1332
1333One or more actual requests are specified in  system elements. The following are examples:
1334\begin{quote}\begin{gsc}\begin{verbatim}
1335<system type='configure' subset=''/>
1336<system type='configure' subset='collectionList'/>
1337<system type='activate' moduleType='collection' moduleName='demo'/>
1338<system type='deactivate' moduleType='site' moduleName='site1'/>
1339\end{verbatim}\end{gsc}\end{quote}
1340
1341The first request reconfigures the whole site---the MessageRouter goes through its whole configure process again. The second request just reconfigures the collectionList---the MessageRouter will delete all its collection information, and re-look through the collect directory and reload all the collections again.
1342The third request is to activate collection demo. This could be a new collection, or a reactivation of an old one. If a collection module already exists, it will be deleted, and a new one loaded. The final request deactivates the site site1---this removes the site from the siteList and module map, and also removes any of that sites collections/services from the static lists.
1343
1344A response just contains a status message\footnote{TODO: add in error/status codes}, for example:
1345\begin{quote}\begin{gsc}\begin{verbatim}
1346<status>MessageRouter reconfigured successfully</status>
1347<status>Error on reconfiguring collectionList</status>
1348<status>collection:demo activated</status>
1349<status>site:site1 deactivated</status>
1350\end{verbatim}\end{gsc}\end{quote}
1351
1352System requests are mainly answered by the MessageRouter. However, Collections and ServiceClusters will respond to a subset of these requests.
1353
1354\subsection{'format'-type messages}\label{sec:format}
1355
1356Collection designers are able to specify how their collection looks to a certain degree. They can specify format statements for display that will apply to the results of a search, the display of a document, entries in a classification hierarchy, for example. This info is generally service specific. All services respond to a format request, where they return any service specific formatting information. A typical request and response looks like this:
1357\begin{quote}\begin{gsc}\begin{verbatim}
1358<request lang="en" to="mgppdemo/FieldQuery" type="format" />
1359
1360<response from="mgppdemo/FieldQuery" type="format">
1361  <format>
1362    <gsf:template match="documentNode"><td><gsf:link>
1363      <gsf:metadata name="Title" />(<gsf:metadata name="Source" />)
1364      </gsf:link></td>
1365    </gsf:template>
1366  </format>
1367</response>
1368\end{verbatim}\end{gsc}\end{quote}
1369
1370The actual format statements are described in Section~\ref{sec:formatstmt}. They are templates written directly in XSLT, or in GSF (GreenStone Format) which is a simple XML representation of the more complicated XSLT templates.
1371GSF-style format statements need to be converted to proper XSLT. This is currently done by the Receptionist (but may be moved to an ActionHelper): the format XML is transformed to XSLT using XSLT with the config\_format.xsl stylesheet.
1372
1373\subsection{'status'-type messages}\label{sec:status}
1374
1375These are only used with process-type services, which are those where a request is sent to start some type of process (see Section~\ref{sec:process}). An initial 'process' request to a 'process' service generates a response which states whether the process had successfully started, and whether its still continuing. If the process is not finished, status requests can be sent repeatedly to the service to poll the status, using the pid to identify the  process.  Status codes are used to identify the state of a process. The values used at the moment are listed in Table~\ref{tab:status codes}\footnote{A more standard set of codes should probably be used, for example, the HTTP codes}.
1376
1377\begin{table}
1378\caption{Status codes currently used in \gsiii\ }
1379\label{tab:status codes}
1380{\footnotesize
1381\begin{tabular}{llp{8cm}}
1382\hline
1383\bf code name & \bf code  & \bf meaning \\
1384& \bf value & \\
1385\hline
1386SUCCESS &  1 & the request was accepted, and the process was  completed \\
1387ACCEPTED & 2 & the request was accepted, and the process has been started, but it is not completed yet \\
1388ERROR & 3 & there was an error and the process was stopped \\
1389CONTINUING & 10 & the process is still continuing \\
1390COMPLETED & 11 & the process has  finished \\
1391HALTED & 12 & the process has stopped  \\
1392INFO & 20 & just an info message that doesn't imply anything \\
1393\hline
1394\end{tabular}}
1395\end{table}
1396
1397 The following shows an example status request, along with two responses, the first a 'OK but continuing' response, and the second a 'successfully completed' response. The content of the status elements in the two responses is the output from the process since the last status update was sent back.
1398
1399\begin{quote}\begin{gsc}\begin{verbatim}
1400<request lang="en" to="build/ImportCollection" type="status">
1401  <paramList>
1402    <param name="pid" value="2" />
1403  </paramList>
1404</request>
1405
1406<response from="build/ImportCollection">
1407  <status code="2" pid="2">Collection construction: import collection.
1408command = import.pl -collectdir /research/kjdon/home/greenstone3/web/sites/
1409    localsite/collect test1
1410starting
1411  </status>
1412</response>
1413
1414<response from="build/ImportCollection">
1415  <status code="11" pid="2">RecPlug: getting directory
1416/research/kjdon/home/greenstone3/web/sites/localsite/collect/test1/import
1417WARNING - no plugin could process /.keepme
1418 
1419*********************************************
1420Import Complete
1421*********************************************
1422* 1 document was considered for processing
1423* 0 were processed and included in the collection
1424* 1 was rejected. See /research/kjdon/home/greenstone3/web/sites/
1425    localsite/collect/test1/etc/fail.log for a list of rejected documents
1426Success
1427  </status>
1428</response>
1429\end{verbatim}\end{gsc}\end{quote}
1430
1431\subsection{'process'-type messages}
1432
1433Process requests and responses  provide  the major functionality of the system---these are the ones that do the actual work. The format depends on the service they are for, so I'll describe these by service.
1434
1435Query type services TextQuery, FieldQuery, AdvancedFieldQuery (GS2MGSearch, GS2MGPPSearch), TextQuery (LuceneSearch)
1436The main type of requests in the system are for services. There are different types of services, currently: \gst{query}, \gst{browse}, \gst{retrieve}, \gst{process}, \gst{applet}, \gst{enrich}. Query services do some kind of search and return a list of document identifiers. Retrieve services can return the content of those documents, metadata about the documents, or other resources. Browse is for browsing lists or hierarchies of documents. Process type services are those where the request is for a command to be run. A status code will be returned immediately, and then if the command has not finished, an update of the status can be requested. Applet services are those that run an applet. Enrich services take a document and return the document with some extra markup added.
1437
1438  Other possibilities include transform, extract, accrete. These types of service generally enhance the functionality of the first set. They may be used during collection formation: 'accrete' documents by adding them to a collection, 'transform' the documents into a different format, 'extract' information or acronyms from the documents, 'enrich' those documents with the information extracted or by adding new information. They may also be used during querying: 'transform' a query before using it to query a collection, or 'transform' the documents you get back into an appropriate form.
1439
1440The basic structure of a service 'process' request is as follows:
1441\begin{quote}\begin{gsc}\begin{verbatim}
1442
1443<request lang='en'  type='process' to='demo/TextQuery'>
1444  <paramList/>
1445  other elements...
1446</request>
1447
1448\end{verbatim}\end{gsc}\end{quote}
1449
1450The parameters are name-value pairs corresponding to parameters that were specified in the service description sent in response to a describe request.
1451
1452\begin{quote}\begin{gsc}\begin{verbatim}
1453<param name='case' value='1'/>
1454<param name='maxDocs' value='34'/>
1455<param name='index' value='dtx'/>
1456\end{verbatim}\end{gsc}\end{quote}
1457
1458Some requests have other content---for document retrieval, this would be a list of document identifiers to retrieve. For metadata retrieval, the content is the list of documents to retrieve metadata for.
1459
1460Responses vary depending on the type of request. The following sections look at the process type requests and responses for each type of service.
1461
1462\subsubsection{'query'-type services}
1463Responses to query requests contain a list of document identifiers, along with some other information, dependent on the query type. For a text query, this includes term frequency information, and some metadata about the result. For instance, a text query on 'snail farming', with the parameter 'maxDocs=10' might return the first 10 documents, and one of the query metadata items would be the total number of documents that matched the query.\footnote{no metadata about the query result is returned yet.}
1464
1465The following shows an example query request and its response.
1466
1467Find at most 10 Sections in the mgppdemo collection, containing the word snail (stemmed), returning the results in ranked order:
1468\begin{quote}\begin{gsc}\begin{verbatim}
1469<request lang='en'  to="mgppdemo/TextQuery" type="process">
1470  <paramList>
1471    <param name="maxDocs" value="10"/>
1472    <param name="queryLevel" value="Section"/>
1473    <param name="stem" value="1"/>
1474    <param name="matchMode" value="some"/>
1475    <param name="sortBy" value="1"/>
1476    <param name="index" value="t0"/>
1477    <param name="case" value="0"/>
1478    <param name="query" value="snail"/>
1479  </paramList>
1480</request>
1481
1482<response from="mgppdemo/TextQuery" type="process">
1483  <metadataList>
1484    <metadata name="numDocsMatched" value="59" />
1485  </metadataList>
1486  <documentNodeList>
1487    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2"
1488    docType='hierarchy' nodeType="leaf" />
1489    <documentNode nodeID="HASH010f073f22033181e206d3b7.2.12"
1490    docType='hierarchy' nodeType="leaf" />
1491    <documentNode nodeID="HASH010f073f22033181e206d3b7.1"
1492    docType='hierarchy' nodeType="interior" />
1493    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.2.2"
1494    docType='hierarchy' nodeType="leaf" />
1495    ...
1496  </documentNodeList>
1497  <termList>
1498    <term field="" freq="454" name="snail" numDocsMatch="58" stem="3">
1499      <equivTermList>
1500        <term freq="" name="Snail" numDocsMatch="" />
1501        <term freq="" name="snail" numDocsMatch="" />
1502        <term freq="" name="Snails" numDocsMatch="" />
1503        <term freq="" name="snails" numDocsMatch="" />
1504      </equivTermList>
1505    </term>
1506  </termList>
1507</response>
1508\end{verbatim}\end{gsc}\end{quote}
1509
1510The list of document identifiers includes some information about document type and node type. Currently, document types include \gst{simple}, \gst{paged} and \gst{hierarchy}. \gst{simple} is for single section documents, i.e. ones with no sub-structure. \gst{paged} is documents that have a single list of sections, while \gst{hierarchy} type documents have a hierarchy of nested sections. For \gst{paged} and \gst{hierarchy} type documents, the node type identifies whether a section is the root of the document, an internal section, or a leaf.
1511
1512The term list identifies, for each term in the query, what its frequency in the collection is, how many documents contained that term, and a list of its equivalent terms (if stemming or casefolding was used).
1513
1514\subsubsection{'browse'-type services}
1515
1516Browse type services are used for classification browsing. The request consists of a list of classifier identifiers, and some structure parameters listing what structure to retrieve.
1517
1518\begin{quote}\begin{gsc}\begin{verbatim}
1519<request lang="en" to="mgppdemo/ClassifierBrowse" type="process">
1520  <paramList>
1521    <param name="structure" value="ancestors" />
1522    <param name="structure" value="children" />
1523  </paramList>
1524  <classifierNodeList>
1525    <classifierNode nodeID="CL1.2" />
1526  </classifierNodeList>
1527</request>
1528
1529<response from="mgppdemo/ClassifierBrowse" type="process">
1530  <classifierNodeList>
1531    <classifierNode nodeID="CL1">
1532      <nodeStructure>
1533    <classifierNode nodeID="CL1">
1534          <classifierNode nodeID="CL1.2">
1535        <classifierNode nodeID="CL1.2.1" />
1536        <classifierNode nodeID="CL1.2.2" />
1537        <classifierNode nodeID="CL1.2.3" />
1538        <classifierNode nodeID="CL1.2.4" />
1539        <classifierNode nodeID="CL1.2.5" />
1540          </classifierNode>
1541    </classifierNode>
1542      </nodeStructure>
1543    </classifierNode>
1544  </classifierNodeList>
1545</response>
1546\end{verbatim}\end{gsc}\end{quote}
1547
1548Possible values for structure parameters are \gst{ancestors}, \gst{parent}, \gst{siblings}, \gst{children}, \gst{descendants}. The response gives, for each identifier in the request, a \gst{<nodeStructure>} element with all the requested structure put together into a hierarchy. The structure may include classifier and document nodes.
1549
1550Structural info can also be requested in the \gst{paramList}, and will be returned in a \gst{<nodeStructureInfo>} element. (See the section on DocumentStructureRetrieve messages.)  Possible values for info parameters are \gst{numSiblings}, \gst{siblingPosition}, \gst{numChildren}.
1551
1552\subsubsection{'retrieve'-type services}
1553
1554Retrieval services are special in that requests are not explicitly initiated by a user from a form on a web page, but are called from actions in response to other things. This means that their names are hard-coded into the Actions. DocumentContentRetrieve, DocumentStructureRetrieve and DocumentMetadataRetrieve are the standard names for retrieval services for content, structure, and metadata of documents. Requests to each of these include a list of document identifiers. Because these generally refer to parts of documents, the elements are called \gst{<documentNode>}. For the content, that is all that is required. For the metadata retrieval service, the request also needs parameters specifying what metadata is required. For structure retrieval services, requests need parameters specifying what structure or structural info is required.
1555
1556Some example requests and responses follow.
1557
1558Give me the Title metadata for these documents:
1559\begin{quote}\begin{gsc}\begin{verbatim}
1560
1561<request lang="en" to="mgppdemo/DocumentMetadataRetrieve" type="process">
1562  <paramList>
1563    <param name="metadata" value="Title" />
1564  </paramList>
1565  <documentNodeList>
1566    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2"/>
1567    <documentNode nodeID="HASH010f073f22033181e206d3b7.2.12"/>
1568    <documentNode nodeID="HASH010f073f22033181e206d3b7.1"/>
1569    ...
1570  </documentNodeList>
1571</request>
1572
1573<response from="mgppdemo/DocumentMetadataRetrieve" type="process">
1574  <documentNodeList>
1575    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2">
1576      <metadataList>
1577        <metadata name="Title">Putting snails in your second pen</metadata>
1578      </metadataList>
1579    </documentNode>
1580    <documentNode nodeID="HASH010f073f22033181e206d3b7.2.12">
1581      <metadataList>
1582        <metadata name="Title">Now you must decide</metadata>
1583      </metadataList>
1584    </documentNode>
1585    <documentNode nodeID="HASH010f073f22033181e206d3b7.1">
1586      <metadataList>
1587        <metadata name="Title">Introduction</metadata>
1588      </metadataList>
1589    </documentNode>
1590  </documentNodeList>
1591</response>
1592\end{verbatim}\end{gsc}\end{quote}
1593
1594One or more parameters specifying metadata may be included in a request. Also, a metadata  value of \gst{all} will retrieve all the metadata for each document.
1595
1596Any browse-type service must also implement a metadata retrieval service to provide metadata for the nodes in the classification hierarchy. The name of it is the browse service name plus \gst{MetadataRetrieve}. For example, the ClassifierBrowse service described in the previous section should also have a ClassifierBrowseMetadataRetrieve service. The request and response format is exactly the same as for the DocumentMetadataRetrieve service, except that \gst{<documentNode>} elements are replaced by \gst{<classifierNode>} elements (and the corresponding list element is also changed).
1597
1598Give me the text (content) of this document:
1599\begin{quote}\begin{gsc}\begin{verbatim}
1600<request lang="en" to="mgppdemo/DocumentContentRetrieve" type="process">
1601  <paramList />
1602  <documentNodeList>
1603    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2" />
1604  </documentNodeList>
1605</request>
1606
1607<response from="mgppdemo/DocumentContentRetrieve" type="process">
1608  <documentNodeList>
1609    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2">
1610      <nodeContent>&lt;Section&gt;
1611       &lt;/B&gt;&lt;P ALIGN=&quot;JUSTIFY&quot;&gt;&lt;/P&gt;
1612       &lt;P ALIGN=&quot;JUSTIFY&quot;&gt;190. When the plants in
1613       your second pen have grown big enough to provide food and
1614       shelter, you can put in the snails.&lt;/P&gt;
1615      </nodeContent>
1616    </documentNode>
1617  </documentNodeList>
1618</response>
1619\end{verbatim}\end{gsc}\end{quote}
1620
1621The content of a node is returned in a \gst{<nodeContent>} element. In this case it is escaped HTML.
1622
1623Give me the ancestors and children of the specified node, along with the number of siblings it has:
1624\begin{quote}\begin{gsc}\begin{verbatim}
1625<request lang="en" to="mgppdemo/DocumentStructureRetrieve" type="process">
1626  <paramList>
1627    <param name="structure" value="ancestors" />
1628    <param name="structure" value="children" />
1629    <param name="info" value="numSiblings" />
1630  </paramList>
1631  <documentNodeList>
1632    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2" />
1633  </documentNodeList>
1634</request>
1635
1636<response from="mgppdemo/DocumentStructureRetrieve" type="process">
1637  <documentNodeList>
1638    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2">
1639      <nodeStructureInfo>
1640        <info name="numSiblings" value="2" />
1641      </nodeStructureInfo>
1642      <nodeStructure>
1643        <documentNode nodeID="HASHac0a04dd14571c60d7fbfd"
1644                docType='hierarchy' nodeType="root">
1645          <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4"
1646                  docType='hierarchy' nodeType="interior">
1647            <documentNode nodeID="HASHac0a04dd14571c60d7fbfd.4.2"
1648                   docType='hierarchy' nodeType="leaf" />
1649          </documentNode>
1650        </documentNode>
1651      </nodeStructure>
1652    </documentNode>
1653  </documentNodeList>
1654</response>
1655\end{verbatim}\end{gsc}\end{quote}
1656
1657Structure is returned inside a \gst{<nodeStructure>} element, while structural info is returned in a \gst{<nodeStructureInfo>} element. Possible values for structure parameters are as for browse services: \gst{ancestors}, \gst{parent}, \gst{siblings}, \gst{children}, \gst{descendants}, \gst{entire}. Possible values for info parameters are \gst{numSiblings}, \gst{siblingPosition}, \gst{numChildren}.
1658
1659\subsubsection{'process'-type services}\label{sec:process}
1660Requests to process-type services are not requests for data---they request some action to be carried out, for example, create a new collection, or import a collection. The response is a status or an error message. The import and build commands may take a long time to complete, so a response is sent back after a successful start to the command. The status may be polled by the requester to see how the process is going.
1661
1662Process requests generally contain just a parameter list. Like for any service, the parameters used by a process-type service can be obtained by a describe request to that service.
1663
1664Here are two example requests for process-services that are part of the build service cluster (hence the addresses all begin with 'build/'), followed by an example response:
1665
1666\begin{quote}\begin{gsc}\begin{verbatim}
1667<request lang='en'  type='process' to='build/NewCollection'>
1668  <paramList>
1669    <param name='creator' value='me@home.com'/>
1670    <param name='collName' value='the demo collection'/>
1671    <param name='collShortName' value='demo'/>
1672  </paramlist>
1673</request>
1674
1675<request lang='en'  type='process' to='build/ImportCollection'>
1676  <paramList>
1677    <param name='collection' value='demo'/>
1678  </paramlist>
1679</request>
1680
1681<response from="build/ImportCollection">
1682  <status code="2" pid="2">Starting process...</status>
1683</response>
1684\end{verbatim}\end{gsc}\end{quote}
1685
1686The \gst{code} attribute in the response specifies whether the command has been successfully stated, whether its still going, etc (see Table~\ref{tab:status codes} for a list of currently used codes). The pid attribute specifies a process id number that can be used when querying the status of this process. The content of the status element is (currently) just the output from the process so far. Status messages, which were described in Section~\ref{sec:status}, are used to find out how the process is going, and whether it has finished or not.
1687
1688\subsubsection{'applet'-type services}
1689
1690Applet-type services are those that process the data for an applet. A request consists only of a list of parameters, and the response contains an \gst{<appletData>} element that contains the XML data to be returned to the applet. The format of this is entirely specific to the applet---there is no set format to the applet data.
1691
1692Here is an example request and response, used by the Phind applet:
1693\begin{quote}\begin{gsc}\begin{verbatim}
1694  <request type='query' to='mgppdemo/PhindApplet'>
1695    <paramList>
1696      <param name='pc' value='1'/>
1697      <param name='pptext' value='health'/>
1698      <param name='pfe' value='0'/>
1699      <param name='ple' value='10'/>
1700      <param name='pfd' value='0'/>
1701      <param name='pld' value='10'/>
1702      <param name='pfl' value='0'/>
1703      <param name='pll' value='10'/>
1704    </paramList>
1705  </request>
1706
1707  <response type='query' from='mgppdemo/PhindApplet'>
1708    <appletData>
1709      <phindData df='9' ef='46' id='933' lf='15' tf='296'>
1710        <expansionList end='10' length='46' start='0'>
1711          <expansion df='4' id='8880' num='0' tf='59'>
1712            <suffix> CARE</suffix>
1713          </expansion>
1714          ...
1715        </expansionList>
1716        <documentList end='10' length='9' start='0'>
1717          <document freq='78' hash='HASH4632a8a51d33c47a75c559' num='0'>
1718            <title>The Courier - N??159 - Sept- Oct 1996 Dossier Investing
1719                   in People Country Reports: Mali ; Western Samoa
1720            </title>
1721          </document>
1722          ...
1723        </documentList>
1724        <thesaurusList end='10' length='15' start='0'>
1725          <thesaurus df='7' id='12387' tf='15' type='RT'>
1726            <phrase>PUBLIC HEALTH</phrase>
1727          </thesaurus>...
1728        </thesaurusList>
1729      </phindData>
1730    </appletData>
1731  </response>
1732
1733\end{verbatim}\end{gsc}\end{quote}
1734
1735\subsubsection{'enrich'-type services}
1736
1737Enrich services typically take some text of documents (inside \gst{<nodeContent>} tags) and returns the text marked up in some way. One example of this is the GatePOSTag service: this identifies Dates, Locations, People and Organizations in the text, and annotates the text with the labels. In the following example, the request is for Location and Dates to be identified.
1738
1739\begin{quote}\begin{gsc}\begin{verbatim}
1740<request lang="en" to="GatePOSTag" type="process">
1741  <paramList>
1742    <param name="annotationType" value="Date,Location" />
1743  </paramList>
1744  <documentNodeList>
1745    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd">
1746      <nodeContent>
1747        FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
1748        Rome 1986
1749        P-69
1750        ISBN 92-5-102397-2
1751        FAO 1986
1752      </nodeContent>
1753    </documentNode>
1754  </documentNodeList>
1755</request>
1756
1757<response from="GatePOSTag" type="process">
1758  <documentNodeList>
1759    <documentNode nodeID="HASHac0a04dd14571c60d7fbfd">
1760      <nodeContent>
1761    FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
1762    <annotation type="Location">Rome</annotation>
1763        <annotation type="Date">1986</annotation>
1764        P-69
1765        ISBN 92-5-102397-2
1766        FAO <annotation type="Date">1986</annotation>
1767      </nodeContent>
1768    </documentNode>
1769  </documentNodeList>
1770</response>
1771\end{verbatim}\end{gsc}\end{quote}
1772
1773\subsection{Page generation}\label{sec:pagegen}
1774
1775A 'page' is some XML or HTML (or other?) data returned in response to an
1776external 'page'-type request. These requests originate from outside \gs\ , for example from a servlet, or Java application, and are received by the Receptionist. As described below in Section~\ref{sec:page-requests}, the requests are XML representations of \gs\  URLs. One of the arguments is action (a). This tells the Receptionist which Action module to pass the request to.
1777
1778Action modules decode the rest of the arguments to determine what requests need to be made to the system. One or more internal requests may be made to the MessageRouter. A request for format information from the Collection/Service may also be made. The resulting data is gathered together into a single XML response, \gst{<page>}, and returned to the Receptionist.
1779
1780The page format is described in Section~\ref{sec:page-format}. The XML may be returned as is, or may be modified by the Receptionist. The various Receptionists are described in Section~\ref{sec:recepts}. The default receptionist used by a servlet transforms the XML into HTML using XSL stylesheets. Section~\ref{sec:collformat} looks at collection specific formatting, in particular for HTML output.
1781Sections~\ref{sec:pageaction} to \ref{sec:systemaction} look at the various actions and what kind of data they gather.
1782
1783\subsubsection{'page'-type requests and their arguments}\label{sec:page-requests}
1784
1785These are requests for a 'page' of data---for example, the home page for a site; the query page for a collection; the text of a document. They contain, in XML, a list of arguments specifying what type of page is required. If the external context is a servlet, the arguments represent the 'CGI' arguments in a \gs\  URL.  The two main arguments are \gst{a} (action) and \gst{sa} (subaction). All other arguments are encoded as parameters.
1786
1787Here are some examples of  requests\footnote{In a servlet context, these correspond to the arguments \gst{a=p\&sa=about\&c=demo\&l=fr}, and \gst{a=q\&l=en\&s=TextQuery\&c=demo\&rt=r\&ca=0\&st=1\&m=10\&q=snail}.}:
1788
1789\begin{quote}\begin{gsc}\begin{verbatim}
1790<request type='page' action='p' subaction='about'
1791         lang='fr' output='html'>
1792  <paramList>
1793    <param name='c' value='demo'/>
1794  </paramList>
1795</request>
1796\end{verbatim}\end{gsc}\end{quote}
1797
1798\begin{quote}\begin{gsc}\begin{verbatim}
1799<request type='page' action='q' lang='en' output='html'>
1800  <paramList>
1801    <param name='s' value='TextQuery'/>
1802    <param name='c' value='demo'/>
1803    <param name='rt' value='r'/>
1804    <!-- the rest are the service specific params -->
1805    <param name='ca' value='0'/> <!-- casefold -->
1806    <param name='st' value='1'/> <!-- stem -->
1807    <param name='m' value='10'/> <!-- maxdocs -->
1808    <param name='q' value='snail'/> <!-- query string -->
1809  </paramList>
1810</request>
1811\end{verbatim}\end{gsc}\end{quote}
1812
1813There are some standard arguments used in Greenstone, and they are described in Table~\ref{tab:args}. These are used by Receptionists and Actions. The GSParams class specifies all the general basic arguments, and whether they should be saved or not (Some arguments need to be saved during a session, and this needs to be implemented outside \gs\  proper --- currently we do this in the servlet, using servlet session handling). The servlet has an init parameter \gst{params\_class} which specifies which params class to use: GSParams can be subclassed if necessary. The Receptionist and Actions must not have conflicting argument names.
1814
1815Other arguments are used dynamically and come from the Services. Service arguments must always be saved during a session. Services may be created by different people, and may reside on a different site. There is no guarantee that there is no conflict with argument names between services and actions. Therefore service parameters are namespaced when they are put on the page, whereas interface (receptionist and action) parameters have no namespace. The default namespace is s1 (service1) --- any parameters that are for the service will be prefixed by this. For example, the case parameter for a search will be put in the page as s1.case, and the resulting argument in a search URL will be s1.case. When actions are deciding which parameters need to be sent in a request to a service, they can use the namespace information.
1816
1817If there are  two or more services combined on a page with a single submit button, they will use namespaces s1, s2, s3 etc as needed. The s  (service) parameter will end up with a list of services. For example, \gst{s=TextQuery,MusicQuery,} and the order of these determines the mapping order of the namespaces, i.e. s1 will map to TextQuery, s2 to MusicQuery.
1818
1819\begin{table}
1820{\footnotesize
1821\begin{tabular}{lll}
1822\hline
1823\bf Argument & \bf Meaning &\bf Typical values \\
1824\hline
1825a & action & a (applet), q (query), b (browse), p (page), pr (process) \\
1826& & s (system)\\
1827sa & subaction & home, about (page action)\\
1828c & collection or  & demo, build \\
1829& service cluster \\
1830s & service name & TextQuery, ImportCollection \\
1831rt & request type & d (display), r (request), s (status) \\
1832ro & response only & 0 or 1 - if set to one, the request is carried out \\
1833& & but no processing of the results is done \\
1834& & currently only used in process actions \\
1835o & output type & XML, HTML, WML \\
1836l & language & en, fr, zh ...\\
1837d & document id & HASHxxx \\
1838r & resource id & ???\\
1839pid & process handle & an integer identifying a particular process request \\
1840\hline
1841\end{tabular}}
1842\caption{Generic arguments that can appear in a \gs\  URL}
1843\label{tab:args}
1844\end{table}
1845
1846\subsubsection{page format}\label{sec:page-format}
1847
1848The basic  page format  is:
1849\begin{quote}\begin{gsc}\begin{verbatim}
1850<page lang='en'>
1851  <pageRequest/>
1852  <pageResponse/>
1853</page>
1854\end{verbatim}\end{gsc}\end{quote}
1855
1856* show configuration and describe whats its used for
1857
1858There are two main elements in the page: pageRequest, pageResponse. The pageRequest is the original request that came into the Receptionist---this is included so that any parameters  can be preset to their previous values, for example, the query options on the query form. The pageResponse contains all the data that has been gathered from the system by the action. The other two elements contain extra information needed by XSLT. Config contains run-time variables such as the location of the gsdl home directory, the current site name, the name of the executable that is running (e.g. library)---these are needed to allow the XSLT to generate correct HTML URLs. Display contains some of the text strings needed in the interface---these are separate from the XSLT to allow for internationalization.
1859
1860The following subsections outline, for each action, what data is needed and what requests are generated to send to the system.
1861
1862
1863Once the XML page has been put together, the page to return to the user is created by transforming the XML using XSLT. The output is HTML at this stage, but it will be possible to generate alternative outputs, such as XML, WML etc. A set of XSLT files defines an 'interface'. Different users can change the look of their web pages by creating new XSLT files for a new 'interface'. Just as we have a sites directory where different sites 'live' (ie where their configuration file and collections are located), we have an interfaces directory where the different interfaces 'live' (ie their transforms and images are located there). The default XSLT files are
1864located in interfaces/default/transforms. Collections, sites and other interfaces
1865can override these files by having their own copy of the appropriate
1866files. New interfaces have their own directory inside interfaces/. Sites and collections can have a transform directory containing XSLT files. The order in which the XSLT files are looked for is collection, site, current
1867interface, default interface.\footnote{this currently breaks down for remote sites - need to rethink it a bit.}
1868[TODO: describe a bit more?? currently only can get this locally]
1869
1870\subsubsection{Receptionists}\label{sec:recepts}
1871
1872The receptionist is the controlling module for the page generation part of \gs\ . It has the job of loading up all the actions, and it knows about the message router it and the actions are supposed to talk to. It routes messages received to the appropriate action (page-type messages) or directly to the message router (all other types). Receptionists also do other things, for example, adding to the page received back from the action any information that is common to all pages.
1873
1874There are different ways of providing an interface to \gs\ , from web based CGI style (using servlets) to Java GUI applications. These different interfaces require slightly different responses from a receptionist, so we provide several standard types of receptionist.
1875
1876Receptionist: This is the most basic receptionist. The page it returns consists of the original request, and the response from the action it was sent to. Methods preProcessRequest, and postProcessPage are called on the request and page, respectively, but in this basic receptionist, they don't do anything.
1877
1878TransformingReceptionist: This extends Receptionist, and overwrites postProcessPage to transform the page using XSLT. An XSLT is listed for each action in the receptionists configuration file, and this is used to transform the page. First, some display information, and configuration information is added to the page. Then it is transformed using the specified XSLT for the action, and returned.
1879
1880WebReceptionist: The WebReceptionist extends TransformingReceptionist. It doesn't do much else except some argument conversion. To keep the URLs short, parameters from the services are given shortnames, and these are used in the web pages.
1881
1882DefaultReceptionist: This extends WebReceptionist, and is the default one for \gsiii\  servlets. Due to the page design, some extra information is needed for each page: some metadata about the current collection. The receptionist sends a describe request to the collection to get this, and appends it to the page before transformation using XSLT.
1883
1884By default, the LibraryServlet uses DefaultReceptionist. However, there is a servlet init-param called \gst{receptionist} which can be set to make the servlet use a different one.
1885
1886\subsubsection{Collection specific formatting}\label{sec:collformat}
1887get format info, transform gsf->xsl. transform xml->html
1888
1889configuration params are passed in to the transformation
1890\subsubsection{CGI arguments}
1891
1892
1893\subsubsection{Page action}\label{sec:pageaction}
1894
1895PageAction is responsible for displaying kinds of information pages, such as the home page of the library, or the home page of a collection, or the help and preferences pages. These pages are not associated with specific services like the other page types. In general, the data comes from describe requests to various modules.
1896The different pages are requested using the subaction argument. For the 'home' page, a 'describe' request is sent to the MessageRouter---this returns a list of all the collections, services, serviceClusters and sites known about. For each collection, its metadata is retrieved via a 'describe' request. This metadata is added into the previous result, which is then added into the page.    For the 'about' page, a \gst{describe} request is sent to the module that the about page is about: this may be a collection or a service cluster.  This returns a list of metadata
1897and a list of services.
1898
1899To get an external html page embedded into a greenstone collection, i.e. a two frame page, with the top frame containing the collection header and navigation bar, and the second frame containg the external page, use subaction html.
1900A url would look like
1901a=p\&amp;sa=html\&amp;c=collname\&amp;url=externalurl
1902
1903\subsubsection{Query action}\label{sec:queryaction}
1904
1905The basic URL is \gst{a=q\&s=TextQuery\&c=demo\&rt=d/r}.
1906There are three query services which have been implemented: TextQuery, FieldQuery, and AdvancedFieldQuery. These are all handled in the same way by query action.
1907For each page, the service description is requested from the  service  of the current collection (via a describe request).  This is currently done every time the query page is
1908displayed, but should be cached. The description includes a list of the parameters available for the query, such as case/stem, max num docs to return, etc. If the request type (rt) parameter is set to d for display, the action only needs to display the form, and this is the only request to the service. Otherwise, the submit button has been pressed, and a query request to the TextQuery service is sent. This has  all the parameters from the URL put into the parameter list. A list of document identifiers
1909is returned. A followup query is sent to the MetadataRetrieve service of the collection: the content includes the list of
1910documents, with a request for some of their metadata. Which metadata to retrieve is determined by looking through the XSLT that will be used to transform the page. The service description and query result are combined into a page of XML, which is returned to the Receptionist.
1911
1912\subsubsection{Applet action}\label{sec:appletaction}
1913
1914There are two types of request to the applet action: \gst{a=a \& rt=d\/} and
1915\gst{a=a \& rt=r\/}.  The value \gst{rt=d\/} means ``display the applet.'' A
1916\gst{describe} request is sent to the service, which returns the \gst{<applet>} HTML element.  The transformation file \gst{applet.xsl} embeds this
1917into the page, and the servlet returns the HTML.
1918
1919The value \gst{rt=r} signals a request from the applet. A process request containing all the parameters is sent to the applet service. The result contains an appletData element, which contains a single  element - this element is returned
1920directly to the applet, in XML. No transformation is done.
1921Because the AppletAction doesn't know or care anything about the applet data, it can work with any applet-service pair.
1922
1923Note that the applet HTML may need to know the name of the \gst{library}
1924program.  However, that name is chosen by the person who installed the software
1925and will not necessarily be ``library''.  To get around this, the applet can
1926put a parameter called ``library'' into the applet data with a null value:
1927\begin{quote}\begin{gsc}\begin{verbatim}
1928<PARAM NAME='library' VALUE=''/>
1929\end{verbatim}\end{gsc}\end{quote}
1930When the AppletAction encounters this parameter it inserts the name of the
1931current library servlet as its value.
1932
1933\subsubsection{Document action}\label{sec:documentaction}
1934
1935DocumentAction is responsible for displaying a document to the user. The display might involve some metadata and/or text for a document or part of a document. For hierarchical documents, a table of contents may be shown, while for paged documents (those with a single linear list of sections), next and previous page buttons may be shown. These different display types require different information about the document. Depending on the arguments, DocumentAction will send requests to several services: DocumentMetadataRetrieve, DocumentStructureRetrieve and DocumentContentRetrieve.
1936
1937A basic display, for example, Title and text, involves a metadata request to get the Title, and a content request to get the text. Hierarchical table of contents display requires a structure request. If the entire contents is to be displayed, the parameter \gst{structure=entire} would be sent in the request. Otherwise, parameters \gst{structure=ancestors}, \gst{structure=children} and possibly \gst{structure=siblings} may be used, depending in the position of the current node in the document. These return a hierarchical structure of nodes, containing ancestor nodes, child nodes and sibling nodes, respectively.
1938For paged display, the structure is not actually needed. A structure request is still sent, but this time it requests some information, rather the structure itself. The information requested includes the number of siblings and the current position of the current node, or the number of children (if the current node is the root of the document).
1939
1940Metadata may be requested for the current node, or for any nodes in the structure, and content also. The metadata and content are added into the appropriate nodes in the structure hierarchy, and this is returned as the page data.
1941
1942\subsubsection{XML Document action}\label{sec:xmldocumentaction}
1943
1944XMLDocumentAction is a little different to the standard DocumentAction. It operates in two modes, \gst{text} and \gst{toc}. In \gst{text} mode, it will retrieve the content of the current document node using a DocumentContentRetrieve request. In \gst{toc} mode, it retrieves the entire table of contents for the document using a DocumentStructureRetrieve request. Either mode may also retrieve metadata for the current section or each section in the table of contents.
1945
1946\subsubsection{GS2Browse action}\label{sec:browseaction}
1947
1948GS2BrowseAction is for displaying \gsii\  style classifiers.
1949\subsubsection{System action}\label{sec:systemaction}
1950
1951SystemAction allows for manual reconfiguration of various components at run-time. There is no interactive web-page displaying the options, it merely turns a set of CGI arguments into an XML system request. The response from a system request is a message which is displayed to the user.
1952
1953\begin{table}
1954\caption{Configure CGI arguments}
1955\label{tab:system-cgi}
1956{\footnotesize
1957\begin{tabular}{ll}
1958\hline
1959\bf arg & \bf description\\
1960\hline
1961a=s & system action\\
1962sa=c$|$a$|$d & type of system request: c (configure), a (add/activate), \\
1963& d (delete/deactivate) \\
1964c=demo &  the request will go to this collection/servicecluster \\
1965& instead of the message router\\
1966ss=collectionList & subset for configure: only reconfigure this part.\\
1967&  For the MessageRouter,  can be serviceClusterList, serviceList, \\
1968& collectionList, siteList.\\
1969&  For a collection/cluster, can be metadataList or serviceList.\\
1970sn=demo & \\
1971st=collection& \\
1972\hline
1973\end{tabular}}
1974\end{table}
1975
1976
1977\subsection{Other code information}
1978
1979Greenstone has a set of Utility classes, which are briefly described in Table~\ref{tab:utils}.
1980
1981\begin{table}[h]
1982\caption{The utility classes in org.greenstone.gsdl3.util}
1983\label{tab:utils}
1984{\footnotesize
1985\begin{tabular}{lp{3.75in}}
1986\hline
1987\bf Utility class & \bf Description\\
1988\hline
1989CollectionClassLoader & ClassLoader that knows about a collection's resource directory \\
1990DBInfo & Class to hold info from GDBM database entry \\
1991Dictionary & wrapper around a Resource Bundle, providing strings with parameters\\
1992GDBMWrapper & Wrapper for GDBM database. Uses JavaGDBM\\
1993GSConstants & holds some constants used for servlet arguments and configuration variables\\
1994GSEntityResolver & an EntityResolver which can be used to find resources such as DTDs\\
1995GSFile & class to create all \gs\  file paths e.g. used to locate configuration files, XSLT files and collection data. \\
1996GSHTML & provides convenience methods for dealing with HTML, e.g. making strings HTML safe\\
1997GSParams & contains names and default values for interface parameters\\
1998GS2Params & a subclass of GSParams which holds default service parameters too, necessary for the gs2 style interface.\\
1999GSPath & used to create, examine and modify message address paths\\
2000GSStatus & some static codes for status messages\\
2001GSXML & lots of methods for extracting information out of \gs\  XML, and creating some common types of elements. Also has static Strings for element and attribute names used by \gs\ .\\
2002GSXSLT & some manipulation functions for \gs\  XSLT\\
2003GlobalProperties & Holds the global properties (from global.properties) \\
2004MacroResolver & Used with replace elements in collection configuration files, replaces a macro or string with another string, metadata or text from a dictionary\\
2005GS2MacroResolver & MacroResolver for GS2 collections, that uses the GDBM database\\
2006Misc & miscellaneous functions\\
2007MyNodeList & A simple implementation of an XML NodeList\\
2008OID & class to handle \gs\  (2) OIDs\\
2009Processing & Runs an external process and prints the output from the process \\
2010SQLQuery & contains a connection to a SQL database, along with some methods for accessing the data, such as converting MG numbers to and from Greenstone OIDs.\\
2011XMLConverter & provides methods to create new Documents, parse Strings or Files into Documents, and convert Nodes to Strings\\
2012XMLTransformer & methods to transform XML using XSLT \\
2013XSLTUtil & contains static methods to be called from within XSLT \\
2014\hline
2015\end{tabular}}
2016\end{table}
2017
2018
2019\newpage
2020\section{Developing \gsiii\ : Adding new features}\label{sec:new-features}
2021
2022[TODO: finish this section ]
2023
2024\subsection{Creating and using new services}\label{sec:new-services}
2025
2026There are three parts to adding new services to \gsiii: defining the new service, specifying that it should be loaded, and using it. If you are talking to \gs\ using the SOAP interface, then the firsttwo  parts are all that need to be done. If you are using the Greenstone servlet interface, then you may need to do work for the third part, depending on what kind of new service it is.
2027If you are adding a service of a type that is already present, for example, a new query service, then the query action can just use your new service as is (assuming it is set up in the same way as the standard query services).
2028However, if it is a new type of service that the interface and actions don't know about, you willl need to add a new action or modify an existing one so that your service is actually used.
2029
2030\subsubsection{Creating the service}
2031
2032You will need to write a new Java class which inherits from \gst{org.greenstone.gsdl3.service.ServiceRack} (or a subclass of this). The class will need to implement at least the \gst{configure}, \gst{process<ServiceName>} and \gst{getServiceDescription} methods. There is a dummy class called \gst{MyNewServicesTemplate.java} in \gst{greenstone3/resources/java} which describes these methods and what needs to be done.
2033
2034\gst{ServiceRack.java} handles the main \gst{process} method. If the request type is 'describe', then it will send back a copy of short\_service\_info, which contains a list of services. If there request type is describe, but for a particular service, then it will call \gst{getServiceDescroption} for that service. For a format request, it will send any format element found in format\_info\_map for that service. For a processing request to a service, then the \gst{process<ServiceName>} method will be called.
2035
2036Once the class is written, it needs to be compiled up and either included in one of the existing jar files, or added in as a jar file to \gst{greenstone3/web/WEB-INF/lib} or a class file to \gst{greenstone3/web/WEB-INF/classes}.
2037
2038\subsubsection{Loading the service}
2039
2040To have the library load in your new service, it needs to be specified in a configuration file somewhere. For a collection service, add a new \gst{<serviceRack>} element to the collection's \gst{buildConfig.xml} file. This element should contain any information that the class needs to configure its service(s). For a site-wide service, add the \gst{<serviceRack>} element to the site's \gst{siteConfig.xml} file, either in the \gst{serviceRackList} or as part of a \gst{serviceCluster}.
2041
2042\subsubsection{Using the service}
2043
2044If you are using the SOAP web service, then you can send an XML request directly to the service. The 'address' of the request will be the service name if it is a site-wide service, cluster-name/service-name if it is site-wide but belonging to a cluster, or collection-name/service-name if it belongs to a collection. You will need to know the format of the XML request and response that the service expects and returns.
2045
2046If you want to access your new service through the current servlet interface that uses actions, then whether you need to do more work or not depends on whatkind of service you have implemented. If you have written a new query or browse service, for example, that has teh same request and response format as the existing services, then you don't need to do anything else. Your collection can just use the new query service straight away.
2047If the service is of an existing type, but needs soemthing different in the request/response format, then you may need to modify an existing action to supply or use the new information.
2048If the service is of a completely new type, then you will probably need a new action to talk to the service and display the results.
2049
2050
2051\subsection{creating new actions/pages}\label{sec:new-pages}
2052
2053\subsection{new interfaces}\label{sec:new-interfaces}
2054
2055It is easy to create new interfaces to \gsiii. Here we are talking about interfaces other than those to display in typical browser.
2056
2057Handheld devices: Use the standard servlet setup, but with a different set of XSLT files to format the pages for small screens, or use WML.
2058
2059Java GUI Interface: There are couple of alternatives. Depending on what you want to display in the GUI, you could talk to either a Receptionist or a MessageRouter. The library classes can be set up and compiled into the GUI program.
2060Talking to a Receptionist will give you access to pages of XML. It is likely that the standard Receptionist class would be used - this doesn't transform the data to HTML. Queries such as ``give me the home page of a collection'' and ``do the following search'' can be issued. All the data needed for the result view is returned. Queries are quite simple, but are limited to what kinds of Actions are available in the library.
2061Talking to a MessageRouter requires a bit more effort on the part of the GUI program, but results in greater flexibility. The kinds of queries that can be issued are individual units of action, such as ``describe yourself'', ``search'', ``retrieve the content for this document''. More than one request may need to be made for a particular feature of the GUI. However you can ask for any combination of data available in the system, you are not relying on Actions. What you will implement though, may be a lot like the Action code in terms of request sequences.
2062
2063Interfaces in other programming languages: Because the communication is all XML based, other interfaces can talk to the Java library if a communication protocol is set up. This could be done using SOAP for example. Like for Java GUI interfaces, the program could talk to a Receptionist or to a MessageRouter.
2064e.g. Java interface. where you can interface to. MR vs Receptionist. different receptionists. e.g., handheld - using servlet, transforming recpt, but new set of XSLT Java program other program - talk to recpt but just get back XML data for pages. Java gui - just talk to MR, do all processing itself.
2065
2066Remote interfaces: remote interfaces can be set up in the same way as above, using a communication protocol between the interface, and the library program.
2067
2068
2069\subsection{New types of collections}\label{sec:new-coll-types}
2070
2071The standard type of collection is built with the \gsii\ Perl collection building system. There are many options to this, but it is conceivable that these options don't meet the needs of all collection builders. \gsiii\  has an ability to use any type of collection you can come up with, assuming some Java code is provided.
2072
2073There are four levels of customization that may be needed with new collections: service, collection, interface XSLT, and action levels. We will use the example collections that come with \gs\  to describe these different levels.
2074
2075Firstly, new service classes need to be written to provide the functionality to search/browse/whatever the collection. If the services have similar interfaces and functionality to the standard services, this may be all that is needed. For example, MGPP collections were the first to be served in \gsiii\ . When we came to do MG collections, all we had to do was write some new service classes that interacted with MG instead of MGPP. Because these collections used the same type of services, this was all we had to do. The format of the configuration files was similar, they just specified MG serviceRack classes rather than MGPP ones.
2076
2077The XML Sample Texts (gberg) collection, however, was done quite differently to the standard collections. New services were provided to search the database (built with Lucene) and to provide the documents and parts of documents (using XSLT to transform the raw XML files). The collectionConfig file had some extra information in it: a list of the documents in the collection along with their Titles. Because the standard collection class has no notion of document lists, a new class was created (org.greenstone.gsdl3.collection.XMLCollection). This class is basically the same as a standard collection class except that it looks for and stores in memory the documentList from the collectionConfig file.
2078
2079To tell \gs\  to load up a different type of collection class, we use another configuration file: \gst{etc/collectionInit.xml}. This specifies the name of the collection class to use.
2080Currently, this is all that is specified in that file, but you may want to add parameters for the class etc.
2081
2082\gst{<collectionInit class="XMLCollection"/>}
2083
2084The display for the collection is also quite different. The home page for the collection  displays the list of documents. To achieve this, the describe response from the collection had to include the list, and a new XSLT was written for the collection that displayed this. Collection XSLT should be put in the transform directory of the collection\footnote{These are currently only used when running \gs\  in a non-distributed fashion, but it will be added in properly at some stage}.
2085
2086Document display is  significantly different to standard \gs\ . There are two modes of display: table of contents mode, and content mode. Clicking on a document link from the collection home page takes the user to the table of contents for the collection. Clicking on one of the sections in the table of contents takes them to a display of that section. To facilitate this, not only do we need new XSLT files , we also needed a new action. XMLDocumentAction was created, that used two subactions, toc and text, for the different modes of display.
2087
2088The Receptionist was told about this new action by the addition of the following element to the interfaceConfig.xml file:
2089
2090\begin{gsc}\begin{verbatim}
2091<action name='xd' class='XMLDocumentAction'>
2092  <subaction name='toc' xslt='document-toc.xsl'/>
2093  <subaction name='text' xslt='document-content.xsl'/>
2094</action>
2095\end{verbatim}\end{gsc}
2096
2097XSLT files are linked to subactions rather than the action as a whole. The collection supplies the two XSLT files written appropriately for the data it contains.
2098
2099All links that link to the documents have to be changed to use the xd action rather than the standard d action. These include the links from the home page, and the links from query results.
2100
2101Querying of the collection is almost the same as usual. The query service provides a list of parameters, does the query and then sends back a list of document identifiers. The standard query action was fine for this collection. The change occurs in the way that the results are displayed---this is accomplished using a format statement supplied in the collectionConfig file inside the search node.
2102
2103\begin{gsc}\begin{verbatim}
2104<search>
2105  <format>
2106    <gsf:template match="documentNode">
2107      <xsl:param name="collName"/>
2108      <xsl:param name="serviceName"/>
2109      <td>
2110        <b><a href="{$library_name}?a=xd&amp;sa=text&amp;c={$collName}&
2111            amp;d={@nodeID}&amp;p.a=q&amp;p.s={$serviceName}">
2112             <xsl:choose>
2113               <xsl:when test="metadataList/metadata[@name='Title']">
2114                 <gsf:metadata name="Title"/>
2115               </xsl:when>
2116               <xsl:otherwise>(section)</xsl:otherwise>
2117             </xsl:choose>
2118           </a>
2119         </b> from <b><a href="{$library_name}?a=xd&amp;sa=toc&amp;
2120           c={$collName}&amp;d={@nodeID}.rt&amp;p.a=q&amp;p.s={$serviceName}">
2121         <gsf:metadata name="Title" select="root"/></a></b>
2122      </td>
2123    </gsf:template>
2124  </format>
2125</search>
2126\end{verbatim}\end{gsc}
2127
2128Instead of displaying an icon and the Title, it displays the Title of the section and the title of the document. Both of these are linked to the document: the section title to the content of that section, the document title to the table of contents for the document. Because these require non-standard arguments to the library, these parts of the template are written in XSLT not \gs\  format language. As is shown here it is perfectly feasible to write a format statement that includes XSLT mixed in with \gs\  format elements.
2129
2130The document display uses CSS to format the output---these are kept in the collection and specified in the collections XSLT files. The documents also specify DTD files. Due to the way we read in the XML files, Tomcat sometimes has trouble locating the DTDs. One option is to make all the links absolute links to files in the collection folder, the other option is to put them in \gs\ 's DTD folder \gst{\$GSDL3SRCHOME/resources/dtd}.
2131
2132\subsection{The gs2 Interface}
2133
2134The library seen at \gst{http://www.greenstone.org/greenstone3/nzdl} is like a mirror to \gst{http://www.nzdl.org}---it aims to present the same collections, in the same way but using \gsiii\  instead of \gsii\ . It uses a new site (nzdl) with a new interface (nzdl) which is based on the gs2 interface. The web.xml file had a new servlet entry in it to specify the combination of nzdl site and nzdl interface.
2135
2136The site was created by making a directory called nzdl in the sites folder. A siteConfig file was created. Because it is running on Linux, we were able to link to all the collections in the old \gs\  installation. The convert\_coll\_from\_gs2.pl script was run over all the collections to produce the new XML configuration files.
2137
2138The gs2 interface was created to be used by this site (and is now a standard part of Greenstone).
2139In many cases, creating a new interface just requires the new images and XSLT  to be added to the new directory(see Sections~\ref{sec:sites-and-ints} and \ref{sec:interface-customise}). This gs2 interface required a bit more customization.
2140
2141The standard \gsiii\  navigation bar lists all the services available for the collection. In \gsii\ , the navigation bar provides the search option, and the different classifiers. This is not service specific, but hard coded to the search and classifiers. The XSLT that produces the navigation bar needed to be altered to produce this.
2142The standard receptionist (DefaultReceptionist) gathers a little bit of extra information for each page of XML before transforming it: this is the list of services for the collection and their display information, allowing the services to be listed along the navigation bar. This is information that is needed by every page (except for the library home page) and therefore is obtained by the receptionist instead of by each action. The nzdl interface uses the classifier list that comes in the ClassifierBrowse service description to display teh list of classifiers.
2143
2144The nzdl interface extends the gs2 interface to provide a different looking home page and an extra static 'gsdl' page.
2145
2146\newpage
2147\section{Distributed \gs\ }\label{sec:distributed}
2148
2149\gs\  is designed to run in a distributed fashion. One \gs\  installation can talk to several sites on different computers. This requires some sort of communication protocol. Any protocol can be used, currently we have a simple SOAP protocol.
2150
2151more explanation..
2152
2153\begin{figure}[h]
2154  \centering
2155  \includegraphics[width=4in]{remote} %5.8
2156  \caption{A distributed digital library configuration running over several servers}
2157  \label{fig:remote}
2158\end{figure}
2159
2160We have used Apache Axis SOAP implementation. This is run as a servlet in Tomcat. Axis is set up during installation of Greenstone. For more details about SOAP in Greenstone, see Appendix~\ref{app:soap}. Debugging soap is described in Appendix~\ref{app:soap-debug}.
2161
2162\subsection{Serving a site using soap}
2163
2164A web service for localsite comes with \gs. However, it is not deployed by default. To deploy it, run run \gst{ant deploy-localsite}. If you want to set up web services for other sites, run \gst{ant soap-deploy-site}. This will prompt you for the sitename (its directory name), and a siteuri - a unique identifier for the web service. Tomcat needs to be running for this to work, and you need to have installed the \gs source code.
2165
2166The ant target deploys the service for the site specified. A resource file (\gst{<sitename>.wsdd}) is created which is used to specify the service. It can be found in \gst{\$GSDL3HOME/resources/soap}, and is generated from \gst{site.wsdd.template}.
2167
2168The address of the new SOAP service will be tomcatserver-address/greenstone3/services/sitename, for example, www.greenstone.org/greenstone3/services/localsite.
2169
2170\subsection{Connecting to a site web service}
2171
2172There are two ways to use a remote site. First, if you have a local site running, then the site can also connect to other remote sites. In the siteConfig.xml file, you need to add a site element into the siteList element.
2173
2174For example, to get siteA to talk to siteB, you need to deploy a SOAP server on siteB, then add a \gst{<site>} element to the \gst{<siteList>} of siteA's \gst{siteConfig.xml} file (in \gst{\$GSDL3HOME/sites/siteA/siteConfig.xml}).
2175
2176In the \gst{<siteList>} element, add the following (substituting the chosen site uri for siteBuri):
2177
2178\begin{gsc}\begin{verbatim}
2179<site name="siteBuri"
2180  address="http://localhost:8080/greenstone3/services/siteBuri"
2181  type="soap"/>
2182\end{verbatim}\end{gsc}
2183
2184(Note that localhost and 8080 should be changed to the values you entered when installing \gsiii. Localhost will only work for servers on the smae machine.).
2185
2186If you have changed the siteConfig.xml file for a site that is running, it will need to be reconfigured. Either restart Tomcat, or reconfigure through a URL:
2187e.g. \gst{http://localhost:8080/greenstone3/library?a=s\&sa=c}.
2188Several sites can be connected to in this manner.
2189
2190The second option is if you have a receptionist set up on a machine where you have no site, and you only want to connect to a single remote site. Instead of using site\_name in the servlet initialisation parameters (in \$GSDL3HOME/WEB-INF/web.xml), you can specify remote\_site\_name, remote\_site\_type and remote\_site\_address. A communicator object will be set up instead of a MessageRouter and the receptionist will talk to the communicator.
2191
2192\appendix
2193
2194\newpage
2195\section{Using \gsiii\  from CVS}\label{app:cvs}
2196
2197\gsiii\  is also available via CVS. You can download the latest version of the code. This is not guaranteed to be stable, in fact it is likely to be unstable. The advantage of using CVS is that you can update the code and get the latest fixes.
2198
2199Note that you will need the Java 2 SDK, version 1.4.0 or higher, and Ant (Apache's Java based build tool, http://ant.apache.org) installed.
2200
2201To check out the \gs\  code, use:
2202
2203\begin{quote}\begin{gsc}\begin{verbatim}
2204cvs -d :pserver:cvs\_anon@cvs.scms.waikato.ac.nz:2402/usr/local/
2205           global-cvs/gsdl-src co -P greenstone3
2206\end{verbatim}\end{gsc}\end{quote}
2207
2208If you need it, the password for anonymous CVS access is \gst{anonymous}. Note that some older versions of CVS have trouble accessing this repository due to the port number being present. We are using version 1.11.1p1.
2209
2210Greenstone is built and installed using Ant (Apache's Java based build tool,
2211http://ant.apache.org). You will need a Java Development
2212Environment (1.4 or higher), and Ant installed to use Greenstone. You can download Ant from \\\gst{http://ant.apache.org/bindownload.cgi}. Make sure that the environment variables JAVA\_HOME and ANT\_HOME are set.
2213
2214In the \gst{greenstone3} directory, you can run \gst{'ant'} which will give you a help message.
2215Running \gst{'ant -projecthelp'} gives a list of the targets that you can run --- these
2216do various things like compile the source code, startup the server etc.
2217
2218The \gst{README.txt} file has up-to-date instructions for installing from CVS. Briefly, for a first time install, run \gst{'ant prepare install'}.
2219
2220The file \gst{build.properties} contains various parameters that can be set by the user. Please check these settings before running the installation process. The install process will ask you if you accept the properties before starting.
2221For a  non-interactive version of the install, run
2222\gst{'ant -Dproperties.accepted=yes install'}
2223
2224To log the output in build.log, run
2225\gst{'ant -Dproperties.accepted=yes -logfile build.log install'}
2226
2227Compilation includes Java and C/C++. On Windows, you will need to have Visual Studio or equivalent installed. Please check the \gst{compile.windows.c++.setup} property in build.properties --- make sure it is set to the setup script of Visual Studio.
2228
2229Note: \gst{gs3-setup} sets the environment variables \gst{GSDL3HOME, GSDL3SRCHOME, CLASSPATH, PATH, JAVA\_HOME} and needs to be done in a shell before doing collection building etc.
2230
2231To run the library, use the \gst{gs3-server.sh/bat} shell scripts.
2232
2233\newpage
2234\section{Tomcat}\label{app:tomcat}
2235
2236Tomcat is a servlet container, and \gsiii\  runs as a servlet inside it.
2237
2238The file \gst{\$GSDL3SRCHOME/packages/tomcat/conf/server.xml} is the Tomcat configuration file. A context for \gsiii\  is given by the file\\ \gst{\$GSDL3SRCHOME/packages/tomcat/conf/Catalina/localhost/greenstone3.xml}. This tells Tomcat where to find the web.xml file, and what URL (\gst{/greenstone3}) to give it. Anything inside the context directory is accessible via Tomcat\footnote{can we use .htaccess files to restrict access??}. For example, the index.html file that lives in \gst{\$GSDL3HOME} can be accessed through the URL \gst{localhost:8080/greenstone3/index.html}. The gs2mgdemo collection's images can be accessed through \\
2239\gst{localhost:8080/greenstone3/sites/localsite/collect/gs2mgdemo/images/}.
2240
2241
2242Greenstone sets up Tomcat to run on port 8080 by default. To change this, you can edit the tomcat.port property in build.properties. If you do this before installing Greenstone, then running 'ant install' will use the new port number. If you want to change it later on, shutdown tomcat, run 'ant configure', then when you restart tomcat it will use the new port.
2243
2244Note: Tomcat must be shutdown and restarted any time you make changes in the following for those changes to take effect:
2245\begin{bulletedlist}
2246\begin{gsc}
2247\item \$GSDL3HOME/WEB-INF/web.xml
2248\item \$GSDL3SRCHOME/packages/tomcat/conf/server.xml
2249\end{gsc}
2250\item any classes or jar files used by the servlets
2251\end{bulletedlist}
2252
2253On startup, the servlet loads in its collections and services. If the site or collection configuration files are changed, these changes will not take effect until the site/collection is reloaded. This can be done through the reconfiguration messages (see Section~\ref{sec:runtime-config}), or by restarting Tomcat.
2254
2255We have disabled following symlinks for the greenstone servlet. To enable it, edit \gst{\$GSDL3SRCHOME/packages/tomcat/conf/Catalina/localhost/greenstone3.xml} and set 'allowLinking' to true.
2256
2257By default, Tomcat allows directory listings. To disable this, change the 'listings' parameter to false in the default servlet definition, in Tomcat's web.xml file (\gst{\$GSDL3SRCHOME/packages/tomcat/conf/web.xml}):
2258
2259We have set the greenstone context to be reloadable. This means that if a class or resource file in web/WEB-INF/lib or web/WEB-INF/classes changes, the servlet will be reloaded. This is useful for development, but should be turned off for production mode (set the 'reloadable' attribute to false).
2260
2261Tomcat uses a Manager to handle HTTP session information. This may be stored between restarts if possible. To use a persistent session handling manager, uncomment the \gst{<Manager>} element in \\
2262\gst{\$GSDL3SRCHOME/packages/tomcat/conf/server.xml}. For the default manager, session information is stored in the work directory:\\
2263\gst{\$GSDL3SRCHOME/packages/tomcat/work/Catalina/localhost/greenstone3/SESSIONS.ser}. Delete this file to clear the cached session info. Note that Tomcat needs to be shutdown to delete this file.
2264
2265\subsection{Proxying Tomcat with apache}
2266
2267Instead of incorporating servlet support into your existing web server, an easy alternative is to proxy Tomcat. The \gst{http://www.greenstone.org/greenstone3} site uses apache to proxy Tomcat. ProxyPass and ProxyPassReverse directives need to be added to the Virtualhost description for the www.greenstone.org server.
2268
2269\begin{quote}\begin{gsc}
2270<VirtualHost xx.xx.xx.xx>\\
2271ServerName www.greenstone.org\\
2272...\\
2273ProxyPass /greenstone3 http://puka.cs.waikato.ac.nz:8080/greenstone3\\
2274ProxyPassReverse /greenstone3 http://puka.cs.waikato.ac.nz:8080/greenstone3\\
2275</VirtualHost>\\
2276\end{gsc}\end{quote}
2277
2278In our example, the \gsiii\  servlet can be accessed at \\
2279\gst{http://www.greenstone.org/greenstone3/library}, instead of at \\
2280\gst{http://puka.cs.waikato.ac.nz:8080/greenstone3/library}, which is not publically accessible.
2281
2282\subsection{Running Tomcat behind a proxy}
2283
2284Almost everything works fine when Tomcat is running behind a proxy. The only time this causes trouble is if the servlet itself needs to make external HTTP connections. We do this in the infomine demo collection for example. One of the service classes sends HTTP requests to the infomine database at riverside. Since this is going through the proxy, a username and password is needed. It is not sufficient to prompt the user for a password because they are unlikely to have a password for the particular proxy that Tomcat is using. What we have done at present is to put a proxy element in the siteConfig.xml file. Here you have to enter a suitable username and password for the proxy server. Unfortunately these are entered in plain text. And the file is viewable via the servlet. So we need a better solution.
2285
2286\newpage
2287\section{SOAP}\label{app:soap}
2288
2289Greenstone uses the Apache Axis SOAP implementation for distributed communications. Axis runs as a servlet inside Tomcat, and SOAP web services can be deployed by this Axis servlet. The Greenstone installation process sets up Axis for Tomcat, but does not deploy any services.
2290
2291To deploy the SOAP service for localsite, run \gst{ant deploy-localsite}.
2292
2293To deploy a SOAP service for other sites, run \gst{ant soap-deploy-site}
2294
2295This will prompt you for the sitename (the site's directory name), and a unique URI for the site. It creates a new SOAPServer class for the site \\(\gst{\$GSDL3SRCHOME/src/java/org/greenstone/gsdl3/SOAPServer<sitename>.java}), creates a resource file for deployment (\gst{\$GSDL3SRCHOME/resources/soap/<sitename>.wsdd}), and then tries to deploy the service.
2296
2297Information about deployed services is maintained between Tomcat sessions---you only need to deploy something once. To undeploy a site, use \gst{ant soap-undeploy-site}.
2298
2299The axis services can be accessed at \gst{localhost:8080/greenstone3/index.jsp}.
2300
2301\subsection{Debugging SOAP}\label{app:soap-debug}
2302
2303If you need to debug the SOAP stuff for some reason, or just want to look at the SOAP messages that are being passed back and forth, you can use the TCP monitor. This intercepts messages coming in to one port, displays them, and passes them to another port.
2304To run it, type:
2305
2306\begin{quote}\gst{java -cp \$GSDL3HOME/WEB-INF/lib/axis.jar \\
2307org.apache.axis.utils.tcpmon}
2308\end{quote}
2309
2310The listen port is the port that you want the monitor to be listening on. It should 'act as' a Listener, with target hostname 127.0.0.1 (localhost), and target port the port that Tomcat is running on (8080). You need to modify the address used to talk to the SOAP service. For example, if you want to monitor traffic between the gateway site and the localsite SOAP server, you will need to edit gateway's siteConfig.xml file and change the port number (in the site element) to whatever you have chosen as the listen port.
2311
2312For example, in the Admin panel of TCPMonitor the Target Hostname might be 127.0.0.1, and the Target Port \# 8080. Set the Listen Port \# to be a different port, such as 8070 and click Add. This produces a new tab panel where you can see the messages arriving at port 8070 before being forwarded to port 8080. You then need to set your test request from your SOAP application to arrive at port 8070 and you will see copies of the messages in the new tab panel.
2313
2314
2315\newpage
2316\section{Tidying up the formatting for imported \gsii\  collections}\label{app:gs2tidy}
2317
2318\subsection{Format statements: \gsii\  vs \gsiii\ }\label{app:gs2format}
2319The following table shows the \gsii\  format elements, and their equivalents in \gsiii\
2320\begin{table}[h]
2321\caption{\gsiii\  equivalents of \gsii\  format statements}
2322{\footnotesize
2323\begin{tabular}{ll}
2324\hline
2325\bf \gsii\         & \bf \gsiii\  \\
2326\hline
2327\gst{[Text]} & \gst{<gsf:text/>} \\
2328\gst{[num]} & \gst{<gsf:metadata name='docnum'/>}\\
2329\gst{[link][/link]} & \gst{<gsf:link></gsf:link>} or \\
2330& \gst{<gsf:link type='document'></gsf:link>}\\
2331\gst{[srclink][/srclink]} & \gst{<gsf:link type='source'></gsf:link>}\\
2332\gst{[icon]} & \gst{<gsf:icon/>} or \\
2333& \gst{<gsf:icon type='document'/>}\\
2334\gst{[srcicon]} & \gst{<gsf:icon type='source'/>}\\
2335\gst{[Title]} (metadata) & \gst{<gsf:metadata name='Title'/>} or \\
2336& \gst{<gsf:metadata name='Title' select='current'/>}\\
2337\gst{[parent:Title]} & \gst{<gsf:metadata name='Title' select='parent' />}\\
2338\gst{[parent(All):Title]} & \gst{<gsf:metadata name='Title' select='ancestors'/>}\\
2339\gst{[parent(Top):Title]} & \gst{<gsf:metadata name='Title' select='root' />}\\
2340\gst{[parent(All': '):Title]} & \gst{<gsf:metadata name='Title' select='ancestors'}\\
2341& \gst{  separator=': ' />}\\
2342\gst{[sibling(All': '):Title]} & \gst{<gsf:metadata name='Title' multiple='true'} \\
2343& \gst{  separator=': ' />}\\
2344\gst{\{Or\}\{[dc.Title],}  & \gst{<gsf:choose-metadata>}\\
2345\gst{  [dls.Title], [Title]\}}& \gst{  <gsf:metadata name='dc.Title'/>}\\
2346& \gst{  <gsf:metadata name='dls.Title'/>}\\
2347& \gst{  <gsf:metadata name='Title'/>}\\
2348& \gst{</gsf:choose-metadata>}\\
2349\gst{\{If\}\{[parent:Title],} & \gst{<gsf:choose-metadata>}\\
2350\gst{  [parent:Title], [Title]\}}& \gst{  <gsf:metadata name='Title' select='parent'/>}\\
2351& \gst{  <gsf:metadata name='Title'/>}\\
2352& \gst{</gsf:choose-metadata>}\\
2353\gst{\{If\}\{[Subject],} & \gst{<gsf:switch>}\\
2354\gst{  <td>[Subject]</td>\}}& \gst{  <gsf:metadata name='Subject'/>}\\
2355& \gst{  <gsf:when test='exists'>} \\
2356& \gst{     <td><gsf:metadata name='Subject'/></td>}\\
2357& \gst{  </gsf:when></gsf:switch>}\\
2358\hline
2359\end{tabular}}
2360\end{table}
2361\subsection{Cleaning up macros}\label{app:gs2replace}
2362
2363Here we show some of the replace items that have been used for \gsii\  collections.
2364
2365Getting rid of silly backslashes:
2366\begin{gsc}\begin{verbatim}
2367<replace scope='text' macro="\\?\\\(" text="\("/>
2368\end{verbatim}\end{gsc}
2369
2370Macro resolving using resource bundles and metadata:
2371\begin{gsc}\begin{verbatim}
2372<replace scope='metadata' macro="_magazines_" bundle="NZDLMacros"
2373   key="Magazines"/>
2374<replace scope='all' macro='_thisOID_' metadata='archivedir'/>
2375<replace macro="_httpcollimg_"
2376   text="sites/localsite/collect/folktale/index/assoc"/>
2377\end{verbatim}\end{gsc}
2378
2379Fixing up broken external links:
2380\begin{gsc}\begin{verbatim}
2381<replace macro="_httpextlink_&amp;rl=1&amp;href="
2382   text="?a=d&amp;c=folktale&amp;s0.ext=1&amp;d="/>
2383<replace macro="_httpextlink_&amp;rl=0&amp;href="
2384   text="?a=p&amp;sa=html&amp;c=folktale&amp;url="/>
2385\end{verbatim}\end{gsc}
2386
2387These two examples show how to deal with \gsii's external link macros. The first one is for a 'relative' external link. In this case, the links are like URL's but they actually refer to Greenstone internal documents. So the \gsiii\  link is to the document, but with parameter s0.ext signifying that the d argument will need translating before retrieving the content.
2388The second example is a truly external link. This is translated into a HTML type page action, where the URL is presented as a frame along with the collection header in a separate frame.
2389
2390Sometimes we need to add in macros to be resolved in a second step:
2391\begin{gsc}\begin{verbatim}
2392<replace macro="_iconpdf_" scope="metadata"
2393   text="&lt;img title='_texticonpdf_' src='interfaces/default/images/ipdf.gif'/&gt;"/>
2394<replace macro="_texticonpdf_" scope="metadata" bundle="interface_gs2"
2395   key="texticonpdf"/>
2396\end{verbatim}\end{gsc}
2397
2398\end{document}
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