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| 4 | <meta http-equiv="Content-Language" content="en-us">
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| 5 | <title>Ant2 feature list</title>
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| 6 |
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| 7 | <style type="text/css">
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| 8 | .comment {
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| 9 | COLOR: #900000;
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| 10 | BACKGROUND: #ffa;
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| 11 | }
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| 14 | </head>
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| 15 |
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| 16 | <body bgcolor="#FFFFFF">
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| 17 |
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| 18 | <p class="comment">If something looks like this, this is either a
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| 19 | request for input or a "REVISIT" marker or similar.</p>
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| 20 |
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| 21 | <h1>Ant2 Goals</h1>
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| 22 |
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| 23 | <p>Even though Ant2 is expected to be incompatible with the
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| 24 | current Ant1 series, it still has the same goals. Ant is a Java
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| 25 | based build tool and this remains the main focus of it. The
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| 26 | original goals of simplicity, understandability and extensibility
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| 27 | still stand and Ant2 will try to achieve them even better than
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| 28 | Ant1 does.</p>
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| 29 |
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| 30 | <h2>Simplicity and Understandability</h2>
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| 31 |
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| 32 | <p>These two goals are closely related. Ant build files shall be
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| 33 | easy to read and understand - at the same time it should be easy
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| 34 | to write a custom Ant task and to use the utility classes that
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| 35 | Ant2 provides.</p>
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| 36 |
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| 37 | <p>Ant2 shall be more consistent than Ant1 is - this means:</p>
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| 38 |
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| 39 | <ul>
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| 40 |
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| 41 | <li>core tasks will use the same attribute names for common
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| 42 | functionality</li>
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| 43 |
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| 44 | <li>similar tasks will be unified to use similar forms.</li>
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| 45 |
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| 46 | <li>different implementations for the same functionality will be
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| 47 | hidden behind facade tasks.</li>
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| 48 |
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| 49 | <li>properties and data types will be unified so that they share
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| 50 | the same namespace and inheritance rules. <i
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| 51 | class="comment">Need to talk about how ${} expansion works for
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| 52 | filesets and so on.</i></li>
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| 53 |
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| 54 | </ul>
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| 55 |
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| 56 | <p>Furthermore some things will have to become more explicit:</p>
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| 57 |
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| 58 | <ul>
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| 59 |
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| 60 | <li>remove all magic properties</li>
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| 61 |
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| 62 | <li>make build file writers explicitly state which
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| 63 | filters/filtersets a copy task will use</li>
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| 64 |
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| 65 | <li>add scoping rules for properties so that not all of them
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| 66 | will be inherited by sub-builds, only those that have been
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| 67 | specified explicitly. <i class="comment">Fill in details once
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| 68 | they've been sorted out.</i></li>
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| 69 |
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| 70 | </ul>
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| 71 |
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| 72 | <p>The front-ends for Ant2 shall be smart enough to automatically
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| 73 | detect the required libraries (like <code>tools.jar</code>), the
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| 74 | use of native scripts shall be kept to a minimum.</p>
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| 75 |
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| 76 | <p>Build file writers can attach a message to targets that will be
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| 77 | presented to the user if that target is going to be skipped (based
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| 78 | on the if/unless attribute of the target).</p>
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| 79 |
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| 80 | <p>Even though Ant installation already is quite simple in Ant1
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| 81 | (extract the archive and set two environment variables),
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| 82 | alternative ways to install Ant like using
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| 83 | <a href="http://java.sun.com/products/javawebstart/">Webstart</a> or
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| 84 | a "self-extracting" JAR file will be explored.</p>
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| 85 |
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| 86 | <h2>Extensibility</h2>
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| 87 |
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| 88 | <p>Ant2 like Ant1 uses build files written in XML as its main
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| 89 | input, but it will not be restricted to it. The core of Ant2 will
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| 90 | work on an object model of Project/Target/Task that is independent
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| 91 | of any external representation.</p>
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| 92 |
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| 93 | <p>As an extension of the current <code><taskdef></code>
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| 94 | concept, tasks can be bundled into task libraries (together with
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| 95 | data types and other utility classes). These task libraries are
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| 96 | special JAR archives that somehow describe the contained tasks to
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| 97 | Ant. Ant will automatically know all tasks contained in task
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| 98 | libraries that have been placed into a special directory - in
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| 99 | addition task libraries can be referenced and used in a build file
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| 100 | explicitly. <i class="comment">Fill in details once they've been
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| 101 | sorted out.</i></p>
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| 102 |
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| 103 | <p>It has become apparent, that several "aspects" of
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| 104 | tasks are so common that task writers find themselves duplicating
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| 105 | code all over again - things like classpath handling or "do
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| 106 | we stop the build if this task fails?" functionality for
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| 107 | example. Ant2 will provide a way to let the user attach an
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| 108 | "aspect handler" to a project - all attributes that live
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| 109 | in a certain namespace are going to be passed to this handler. <i
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| 110 | class="comment">Need to talk about TaskContext here.</i></p>
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| 111 |
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| 112 | <p>Ant2 will farm out common functionality from tasks into utility
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| 113 | classes so that task writers can benefit from a tested and stable
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| 114 | framework - they shouldn't need to deal with existing tasks
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| 115 | directly (like some tasks "abuse" the
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| 116 | <code><touch></code> task in Ant1).</p>
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| 117 |
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| 118 | <p>Ant2 will provide a way to define tasks that itself can have
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| 119 | tasks as child elements without knowing all defined tasks at
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| 120 | compile time. Discussions on ant-dev usually talk about
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| 121 | "container tasks" in this context.</p>
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| 122 |
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| 123 | <p>The only way to "include" common XML snippets so far
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| 124 | has been the usage of external SYSTEM entities, a mechanism that
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| 125 | is tied to DTDs and doesn't mix well with alternative
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| 126 | approaches like XML Schema. Ant2 will provide a built-in include
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| 127 | mechanism.</p>
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| 128 |
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| 129 | <h1>New/Modified Features</h1>
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| 130 |
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| 131 | <p>Ant2 will run the build process fully dynamically, which means
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| 132 | that task won't be instantiated before they are actually being run
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| 133 | and <code>${}</code> expansion will see the very latest value of a
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| 134 | property. It will be possible to reassign values of properties via
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| 135 | a built-in task.</p>
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| 136 |
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| 137 | <h2>Compatibility with Ant1</h2>
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| 138 |
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| 139 | <p>Ant2 is going to break Ant1 in several ways:</p>
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| 140 |
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| 141 | <ul>
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| 142 |
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| 143 | <li>Tasks written for Ant1 won't work in Ant2 as the API of
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| 144 | Ant's core and the names of utility classes are going to
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| 145 | change. There will probably be adaptors and utility classes to
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| 146 | ease the transition for task writers.</li>
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| 147 |
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| 148 | <li>Build files written for Ant1 will probably not be valid in
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| 149 | Ant2 or at least not yield the same results. It is expected that
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| 150 | Ant2 will come with a tool to translate Ant1 build files into
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| 151 | equivalent Ant2 versions</li>
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| 152 |
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| 153 | <li>magic properties like <code>build.compiler</code> may
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| 154 | disappear and be replaced by a different customization
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| 155 | concept.</li>
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| 156 |
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| 157 | <li>Ant2 is going to require a JDK version 1.2 or above and a
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| 158 | JAXP compliant parser version 1.1 or above.</li>
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| 159 |
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| 160 | <li>If you specify more than one target in another target's
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| 161 | depends attribute, Ant1 will execute these targets from left to
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| 162 | right (as long as the dependency tree permits it) - Ant2 will
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| 163 | not guarantee this behavior but will allow build file writers to
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| 164 | specify the order explicitly.</li>
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| 165 |
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| 166 | <li>Dereferencing a non existent property a via ${a} will result
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| 167 | in a build failure.</li>
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| 168 |
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| 169 | </ul>
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| 170 |
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| 171 | <h2>Support Integration of Ant Into Other Tools</h2>
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| 172 |
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| 173 | <p>Ant2 will have a clear separation between the front-end that is
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| 174 | responsible for user interactions, the object model that
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| 175 | represents the project to build and the part of Ant that runs the
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| 176 | build process itself <i class="comment">Name that TaskEngine,
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| 177 | ProjectEngine, ExecutionEngine or what?</i>. This separation is
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| 178 | expected to ease the integration of Ant (or parts of it) into
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| 179 | other products.</p>
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| 180 |
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| 181 | <p>Ant2 itself will include a command line front-end and Antidote
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| 182 | will become the GUI front-end to it. Other front-ends like a
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| 183 | servlet front-end are expected <i class="comment">outside of
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| 184 | Ant's core</i> as well.</p>
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| 185 |
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| 186 | <p>In addition to this separation, the following features should
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| 187 | help people who want to integrate Ant into their products:</p>
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| 188 |
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| 189 | <ul>
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| 190 |
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| 191 | <li>It will be possible to cancel a running build process.</li>
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| 192 |
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| 193 | <li>Ant will detach from <code>System.err/.out/.in</code>
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| 194 | completely and communicate with the front-end via a well defined
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| 195 | API. The front-end will have to handle user input for tasks
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| 196 | that need it (tasks that ask for a password for example).</li>
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| 197 |
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| 198 | <li>Tasks will provide some way to identify their attributes
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| 199 | from the outside. <i class="default">fill in details</i></li>
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| 200 |
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| 201 | </ul>
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| 202 |
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| 203 | <h2>More Control for Users and Build File Writers</h2>
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| 204 |
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| 205 | <p>Ant2 will use a <code>BuildListener</code> concept similar to
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| 206 | the one of Ant1 but may provide a richer set of events. It will be
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| 207 | possible to attach and detach listeners to a build process from
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| 208 | within the build file and to modify the behavior of attached
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| 209 | listeners.</p>
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| 210 |
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| 211 | <p>In Ant1 users have little control over how things work. There
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| 212 | are a couple of magic properties to make Ant chose a preferred
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| 213 | compiler or modify the CLASSPATH, but they are barely documented.
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| 214 | If users want to set these properties for every build process,
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| 215 | they have to learn the undocumented tricks of the
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| 216 | <code>ANT_OPTS</code> environment variable or the
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| 217 | <code>~/.antrc</code> file.</p>
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| 218 |
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| 219 | <p>Ant2 will have a well defined system to specify user
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| 220 | preferences. This system will not only let user chose their
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| 221 | compiler but also give them a chance to provide default values for
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| 222 | attributes (say you always want the <code>debug</code> attribute
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| 223 | of the <code>javac</code> task to be true - unless it has been
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| 224 | disabled explicitly). <i class="comment">Need to give details once
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| 225 | they've been sorted out.</i></p>
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| 226 |
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| 227 | <h2>Documentation System</h2>
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| 228 |
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| 229 | <p>All tasks will be documented in XML files using a common DTD <i
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| 230 | class="comment">Still need to define it</i> - task libraries are
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| 231 | expected to include the documentation using this DTD inside the
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| 232 | library itself.</p>
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| 233 |
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| 234 | <h2>Better Subbuild Handling</h2>
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| 235 |
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| 236 | <p class="comment">Is there something beyond "should become
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| 237 | better" right now?</p>
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| 238 |
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| 239 | <h2>Data Types</h2>
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| 240 |
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| 241 | <p>Ant1 supports a limited set of data types (fileset, patternset
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| 242 | and path) and at least up to Ant 1.3 it is not possible to
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| 243 | register custom data types without writing a task that does this.
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| 244 | Ant2 will provide a built-in mechanism to define new data
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| 245 | types.</p>
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| 246 |
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| 247 | <p>Existing data-types will be improved, the files in a fileset
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| 248 | can be chosen based on more than just pattern matching for example
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| 249 | (modification time or permissions for example). Ant2 will have
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| 250 | built-in tasks for set operations.</p>
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| 251 |
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| 252 | <p>Data types and properties will share the same name space and
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| 253 | follow the same scoping and precedence rules.
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| 254 | <i class="comment">${} again.</i></p>
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| 255 |
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| 256 | <h2>Multi-Threading of Tasks Within a Target</h2>
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| 257 |
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| 258 | <p>It will be possible to run several tasks in parallel - these
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| 259 | tasks will belong to the same target and all tasks will be joined
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| 260 | at the end of the target.</p>
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| 261 |
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| 262 | <h2>Internationalization</h2>
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| 263 |
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| 264 | <p>Ant2 itself will provide internationalized (error) messages and
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| 265 | provide utility classes to help task writers to do the same.
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| 266 | <i class="comment">These utility classes may very well come from a
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| 267 | different (Jakarta) project</i>.</p>
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| 268 |
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| 269 | <p>Ant's primary language and the language of the build file
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| 270 | will continue to be English.</p>
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| 271 |
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| 272 | <h1>Rejected Features</h1>
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| 273 |
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| 274 | <p>This is list is not complete, it just highlights some of the
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| 275 | rejected features and tries to explain why they've been
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| 276 | rejected. Two very common reasons to reject something were, that
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| 277 | the request has been too vague or the same functionality could
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| 278 | already be provided by some other accepted new feature.</p>
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| 279 |
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| 280 | <p>For a complete listing of all requested features, see <a
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| 281 | href="requested-features.html">requested-features.html</a>. The
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| 282 | discussion on all topics can be followed in the <a
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| 283 | href="http://marc.theaimsgroup.com/?l=ant-dev&r=1&w=2">archives
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| 284 | for ant-dev</a> in threads starting from 2001-03-21 - the subject
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| 285 | lines contained either <code>[VOTE]</code> or
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| 286 | <code>[DISC]</code>.</p>
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| 287 |
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| 288 | <h2>Simple Flow-Control</h2>
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| 289 |
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| 290 | <p>People asking for these kind of things have often heard the
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| 291 | standard "Ant shall not become yet another scripting language, Ant
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| 292 | shall not fall into the same traps make/Perl did ..." response
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| 293 | from the committers and some long-term ant-dev people.</p>
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| 294 |
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| 295 | <p>The long version of that answer is:</p>
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| 296 |
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| 297 | <ul>
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| 298 | <li>There are lots of open source scripting languages, there is
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| 299 | no need to define a new one.</li>
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| 300 |
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| 301 | <li>Ant has been created to be a build tool. While you can use
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| 302 | it for a whole lot of other things, this is not Ant's primary
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| 303 | focus (and it shouldn't be). Most use-cases that ask for
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| 304 | flow-control are out of Ant's scope.</li>
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| 305 |
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| 306 | <li>Ant already provides the requested functionality for many
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| 307 | common situations. The execon and apply tasks can be used to
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| 308 | iterate over a set of files as the (planed for Ant2) javaon and
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| 309 | anton tasks will do.</li>
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| 310 |
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| 311 | <li>Providing flow-control inside Ant's core would increase the
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| 312 | complexity of this core. This would make it difficult for new
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| 313 | contributors to understand how Ant works and increase the
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| 314 | maintenance cost for Ant at the same time. The goal of the Ant
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| 315 | developers is to push as much complexity and functionality out
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| 316 | of Ant's core into the tasks as possible.</li>
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| 317 | </ul>
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| 318 |
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| 319 | <p>That being said, Ant2 will make it easy to write iteration or
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| 320 | conditional tasks via the new container task concept. We expect
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| 321 | foreach, switch and if tasks to be written, but they will probably
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| 322 | not become core parts of the Ant distribution.</p>
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| 323 |
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| 324 | <h2>Advanced Conditionals for if/unless Attributes</h2>
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| 325 |
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| 326 | <p>The argument here is the same as for flow-control. We are
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| 327 | talking about complexity that can be pushed from the core to tasks
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| 328 | - and that is what will be done. Instead of additional power for
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| 329 | the if/unless attributes, Ant2 will have a new task that can set
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| 330 | properties based on the values of other properties or logical
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| 331 | combinations of other conditions, something like (making up
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| 332 | syntax):</p>
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| 333 |
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| 334 | <pre>
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| 335 | <condition name="javamail-complete">
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| 336 | <and>
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| 337 | <available class="javax.mail.Transport"/>
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| 338 | <available class="javax.activation.DataHandler"/>
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| 339 | </and>
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| 340 | </condition>
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| 341 | </pre>
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| 342 |
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| 343 | <p>will become possible</p>
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| 344 |
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| 345 | <h2>Multi-Threaded Execution of Targets</h2>
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| 346 |
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| 347 | <p>The general feeling was, that the combination of target
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| 348 | dependencies and multi-threading would soon become too complex,
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| 349 | especially since Ant2 will allow people to explicitly enforce the
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| 350 | order in which (independent) targets will be executed.</p>
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| 351 |
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| 352 | <p>This issue will be explored again later, it has not been
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| 353 | rejected for all time being, but it is out of scope for
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| 354 | Ant 2.0</p>
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| 355 |
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| 356 | <h1>Ideas for New Tasks and Tools</h1>
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| 357 |
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| 358 | <p>Please refer to <a
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| 359 | href="requested-features.html">requested-features.html</a> in the
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| 360 | section "I. Things that don't affect the core but are
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| 361 | requests for new tasks or enhancements to existing tasks."
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| 362 | for this.</p>
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| 363 |
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| 364 | <hr>
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| 365 | <p align="center">$Id: features.html,v 1.6 2001/10/31 07:59:07 bodewig Exp $</p>
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| 366 | <p align="center">Copyright © 2001 Apache Software
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| 367 | Foundation. All rights Reserved.</p>
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| 368 | </body>
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| 369 | </html>
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