Installation of this extension follows the usual pattern:

  ./CASCADE-MAKE.sh


For interative experiments with the Triplestore, you can then visit
the home page:

  http://localhost:3030/

Go to the control panel:

  http://localhost:3030/control-panel.tpl

The control panel lets you choose which dataset to work with through a
drop-down menu.  For the Greenstone extension installation there
should only be one:

  /greenstone

Pressing 'select' triggers a POST action to:

  http://localhost:3030/$/dataset
  
which triggers a redirect (through setting 'Location:' in the respose header) to:


  http://localhost:3030/sparql.tpl


A generic query to try out is:

  select * where { ?s ?p ?o } limit 100


#----
# ReverseProxying
#----

If serving your Greenstone3 through a public facing web server, such as Apache2,
then the installed '.tpl' files and the Location redirects don't work.  Introducing
a base tag into the header such as:

<base href="/greenstone3-lod/" />

and changing the 'control-panel.tpl' form action to be:

 <form action="/greenstone3-lod/${action}" method="post">
 
helps a bit, but the Location redirect is still an issue.

Bottom-line to run a SPARQL query directly, (for localhost) you would do:

  http://localhost:3030/greenstone/query?query=select+*+where+%7B+%3Fs+%3Fo+%3Fp+%7D+limit+100&output=text&stylesheet=

For a proxied install you would (continuing the example) do:

http://sowemustthink.space/greenstone3-lod/greenstone/query?query=select+*+where+%7B+%3Fs+%3Fo+%3Fp+%7D+limit+100&output=text&stylesheet=


Factoring in these details, it is possible to setup a transform/page/sparql.xsl page in Greenstone3 this is fully operational,
even in the ReverseProxying situation.

One key step in sparql.xsl is to updated the form input argument for 'stylesheet' to specify the proxied prefix URL:

  stylesheet=/greenstone3-lod/xml-to-html-links.xsl
  stylesheet=%2Fgreenstone3-lod%2Fxml-to-html-links.xsl


When asking for the SPARQL XML result to be transformed to html-links, the hyperlinks in the page generated
also need some tweaking.  The Greenstone3 sparql.xsl page helps plumb the static files used back to the
/greenstone3-lod/ url, but inside 'xml-to-html-links.xsl' this sets another 'stylesheet=' argument that
needs to be updated to the ReverseProxy setup


    <a href="?query={$query}&amp;output=xml&amp;stylesheet=%2Fxml-to-html-links.xsl">
->    
    <a href="?query={$query}&amp;output=xml&amp;stylesheet=%2Fgreenstone3-lod%2Fxml-to-html-links.xsl">

You might need to reload the xml-to-html-links.xsl file in the browser if it has been cached before the change


% fgrep -rl xml-to-html etc/
  etc/pages/sparql.html
  etc/pages/sparql.tpl
  etc/pages/xml-to-html-links.xsl




#----
# Note about Jena code:
#----

  Jena is a pure Java code base, and the relevant compiled jar files
  are bundled with this extension, so no actual compilation is needed.
  The main task CASCADE-MAKE.sh does is to untar the 'binary' files,
  and setup them up in appropriate top-level ' lib' folder (for jar
  files) etc so Greenstone can find them

  In case it is ever needed, the companion source code is in 'src'
  directory (taken from the Apache Jena website, matched to the binary
  version).  For source code, there was only a zip version of the file
  to download.

   To run the command-line client programs, such as 's-put', this
   requires Ruby to be installed.  The source code for this is
   provided in the 'packages' directory, and compiled up and installed
   as part of running ./CASCADE-MAKE.sh