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<h1> Eclipse-based Products and Extensions</h1>
<p>Last modified 15:00 Thursday May 9, 2002</p>
<p>Eclipse technology is the foundation of, and provides building blocks for,
products aimed at the software development tools market. Commercial software
vendors are expected to build, brand, and package products using the Eclipse
platform as the nucleus, to sell these products into the development tools
marketplace, and to support them once in the field.</p>
<p>The Eclipse platform itself is not a &quot;product&quot; in any of these
senses. Eclipse is an open source project that provides raw ingredients without
box, label, or price tag. The closest that the Eclipse project gets to a
packaged form is the Eclipse SDK, which can be downloaded from <a href="http://www.eclipse.org">eclipse.org</a>,
installed, and used as a full-service Java IDE which also happens to include
special support for developing Eclipse plug-ins (PDE).</p>
<p>This note describes how the Eclipse platform is designed to be turned into products.
The license governing the Eclipse platform gives a software vendor almost
complete freedom over how to built a product. So anyone building a product is
free to ignore this advice. However, as is often the case with standards,
adhering to the same rules as everyone else has its rewards: it fosters greater
interoperability between products, and makes it easier for the end user because
different products behave in similar ways.</p>
<p>Eclipse plug-ins are intended to packaged and delivered to the customer into
one of two forms: either as self-contained Eclipse-based products, or as add-on
extensions to Eclipse-based products. We'll first explain what we mean by
Eclipse-based product since it is the more basic notion.</p>
<h2>Eclipse-based products</h2>
<p>An Eclipse-based <b>product</b> is a stand-alone program build with Eclipse.
Products are self-contained in that all code and plug-ins needed to get up and
running are included; this includes a Java runtime environment (JRE), and the
code for the Eclipse platform itself. After installing a product on a computer
with a conventional native installer, the user launches the product (via its
product executable) and is presented with an Eclipse workbench configured
appropriately for the purposes that product was designed to support (be it
developing enterprise web servers, developing C++ programs, or developing
whatever). Products are intended to be updated, either with a conventional
native installer, or with the build-in Eclipse update manager, which is always
available to the user from the Eclipse workbench (&quot;Update Manager&quot; on
the &quot;Help&quot; menu).</p>
<p>If we looked more closely at how the Eclipse parts of the product are
organized, we would see that all plug-ins that go into a product are grouped
into <b>features</b>. &quot;Feature&quot; is an Eclipse update manager notion: a
feature is the smallest unit of separately downloadable and installable
functionality. Features also play a secondary role in how the Eclipse platform
runs.</p>
<p>To make things a bit more concrete, the top level structure of an installed
Eclipse-based product looks like this (italics indicate product-specific file
names):&nbsp;</p>
<p><code>&lt;<i>install</i>&gt;/<br>
&nbsp; <i>acmeproduct</i>.exe&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </code>product
executable<code><br>
&nbsp;
eclipse/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>container for installed Eclipse files<code><br>
&nbsp;&nbsp;&nbsp; .eclipseproduct&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </code>marker
for Eclipse product install<code><br>
&nbsp;&nbsp;&nbsp; eclipse.exe&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse executable launcher<code><br>
&nbsp;&nbsp;&nbsp; startup.jar&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse Java launcher<code><br>
&nbsp;&nbsp;&nbsp; install.ini&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>install info<code><br>
&nbsp;&nbsp;&nbsp; .config/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>install info (computed at install time with -initialize option)<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; platform.cfg&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>default platform configuration<code><br>
&nbsp;&nbsp;&nbsp; jre/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Java runtime environment (JRE)<code><br>
&nbsp;&nbsp;&nbsp;
features/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>installed feature versions<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.acme.acmefeature</i>_<i>1.0.0</i>/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>primary feature for product<code><br>
&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; feature.xml&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>feature manifest file<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; org.eclipse.platform_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>feature for Eclipse platform<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; org.eclipse.platform.win32_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>feature for Eclipse platform<code><br>
&nbsp;&nbsp;&nbsp; plugins/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>installed plug-ins and fragment versions<code><br>
</code>&nbsp;<code>&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.acme.acmefeature</i>_<i>1.0.0</i>/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>product-specific plug-in<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; plugin.xml&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>plug-in manifest file<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; about.ini&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>about info for product<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <i>acme</i>.gif&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>window icon for product<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; plugin_customization.ini&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>about info for product<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; splash.png&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>product splash screen<code><br>
</code>&nbsp; <code>&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.acme.myplugin</i>_<i>1.0.0</i>/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>product-specific plug-in <code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; plugin.xml&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>plug-in manifest file <code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <i>myplugin</i>.jar&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>code for product-specific plug-in<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; org.eclipse.platform_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse platform plug-in<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; org.eclipse.platform.win32_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse platform plug-in<code><br>
&nbsp;&nbsp;&nbsp; &nbsp; org.eclipse.core.boot_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse platform plug-in<code><br>
&nbsp; &nbsp;&nbsp;&nbsp; org.eclipse.core.runtime_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse platform plug-in<code><br>
&nbsp; &nbsp;&nbsp;&nbsp; org.eclipse.core.resources_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse platform plug-in<code><br>
&nbsp;&nbsp;&nbsp; &nbsp; org.eclipse.ui_2.0.0/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>Eclipse platform plug-in<code><br>
&nbsp; &nbsp;&nbsp;&nbsp; (more org.eclipse.* plug-in directories)<br>
&nbsp;&nbsp;&nbsp;
links/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>links to extensions (see next section)<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.wiley.anvilfeature</i>.link&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>link to separately-installed extension<code><br>
</code></p>
<p>Each product should partition its own plug-ins into one or more features. The
Eclipse platform itself is partitioned into three major features, Platform, JDT,
and PDE. There are also a bunch of lesser features, including documentation,
examples, and OS-dependent portions of Platform. The binary distribution of the
Eclipse 2.0 release makes each of these features available as a separate zip.
This allow a product packager to download and unzip just the pieces needed for a
particular product offering.</p>
<p>To the user, an installed product usually shows up on the desktop as a
shortcut. Opening the shortcut starts the product. For a simple product that
does nothing other than run an Eclipse workbench, the shortcut target is the
Eclipse executable launcher (<code>&lt;<i>install</i>&gt;/eclipse/eclipse.exe</code>).
For products that have other things to do as well, the shortcut targets the
product's own executable (<code>&lt;<i>install</i>&gt;/<i>acmeproduct</i>.exe</code>),
which invokes <code>eclipse.exe</code> at some point.</p>
<p>Whenever the Eclipse platform is run, exactly one feature gets to control the
overall personality of the Eclipse platform. This is the called the product's <b>primary
feature</b>, and it controls highly visible things including the splash screen,
window branding images, the about box, the welcome page, the default
perspective, and customization of the default settings of plug-in preferences.
Strictly speaking, a product could have more than one primary feature; the
selection of which primary feature gets control is done via the <code>-feature</code>
command line option to&nbsp; <code>eclipse.exe</code>. The typical product has
just one eligible primary feature.</p>
<p>Summary of characteristics of products:</p>
<ul>
  <li>a product is installed in a single directory tree</li>
  <li>a product includes copies of the org.eclipse.* plug-ins that it needs</li>
  <li>OS-dependent code for multiple operating environment can sit side-by-side
    in a product install</li>
  <li>a products is installed and uninstalled by a native installer only</li>
  <li>more than one product may be installed on the same computer</li>
  <li>a product is installed, updated, and uninstalled independently of other
    Eclipse-based products</li>
  <li>a product is updated by a native installer or by the Eclipse update
    manager</li>
  <li>a product can have one or more primary features, and any number of other
    features</li>
  <li>a primary feature determines the Eclipse workbench overall appearance and
    personality</li>
  <li>a dominant primary feature must be selected for each run</li>
  <li>the update manager can update the features and plug-ins installed with the
    product</li>
  <li>the update manager can install and configure additional features and
    plug-ins into the product</li>
</ul>
<h2>Extensions to Eclipse-based products</h2>
<p>An <b>extension</b> is bundle of Eclipse-based features designed to be
installed separately and used with any Eclipse-based product. In contrast to a product,
an extension includes neither eligible primary features, nor a copy of the Eclipse platform, nor its own JRE.</p>
<p>The same installed base of files for an extension can be used from several
Eclipse-based products. This means an extension only needs to be updated in one
place, while having the updated features available to all products linked to that extension.</p>
<p>To keep things concrete, the top level structure of an installed
Eclipse-based extension looks like this:&nbsp;</p>
<p><code>&lt;<i>extension install</i>&gt;/<br>
&nbsp;
eclipse/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>container for installed Eclipse files<code><br>
&nbsp;&nbsp;&nbsp; .eclipseextension&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </code>marker
for Eclipse extension install<code><br>
&nbsp;&nbsp;&nbsp;
features/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>installed feature versions<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.wiley.anvilfeature</i>_<i>1.0.0</i>/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>feature for extension<code><br>
&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; feature.xml&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>feature manifest file<code><br>
&nbsp;&nbsp;&nbsp; plugins/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>installed plug-ins and fragment versions<code><br>
</code>&nbsp;<code>&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.wiley.anvilfeature</i>_<i>1.0.0</i>/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>extension-specific plug-in<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; plugin.xml&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>plug-in manifest file<code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; about.ini&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>about info for feature<code><br>
</code>&nbsp; <code>&nbsp;&nbsp;&nbsp;&nbsp; <i>com.example.wiley.otherplugin</i>_<i>1.0.0</i>/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>extension-specific plug-in <code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; plugin.xml&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>plug-in manifest file <code><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <i>otherplugin</i>.jar&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</code>code for extension-specific plug-in</p>
<p>Characteristics of extensions:</p>
<ul>
  <li>an extension is installed in a single directory tree (separate from
    products or other extensions)</li>
  <li>an extension does not include a copy of the Eclipse platform plug-ins, a
    JRE, or an executable</li>
  <li>OS-dependent code for multiple operating environment can sit side-by-side
    in an extension install</li>
  <li>an extension is installed and uninstalled by a native installer only</li>
  <li>more than one extension may be installed on the same computer</li>
  <li>an extension is installed, updated, and uninstalled independently of other
    Eclipse-based products</li>
  <li>an extension is updated by a native installer or by the Eclipse update
    manager</li>
  <li>a product can have one or more features</li>
  <li>an extension does not define primary features</li>
  <li>to be useful, an extension must be associated with an Eclipse-based
    product</li>
  <li>an extension can be associated with one or more products at the time the
    extension is installed</li>
  <li>an extension can be associated with a product via the update manager</li>
  <li>the update manager can update the features and plug-ins installed with the
    extension</li>
  <li>the update manager can install and configure additional features and
    plug-ins into the extension</li>
</ul>

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