2002-09-04 11:47:40 -04:00
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<title>Expat Development Roadmap</title>
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border="0"/></a></td>
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<td class="banner"><h2>Expat Development Roadmap</h2></td>
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<td class="content">
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<h2>PROPOSAL</h2>
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2002-09-05 16:18:45 -04:00
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<p><em>Updated 5 September 2002.</em></p>
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2002-09-04 23:08:01 -04:00
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2002-09-04 11:47:40 -04:00
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<p>This is a proposed roadmap for the further development of Expat. The
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primary purpose for making this proposal is to determine whether our
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ideas for continued development are aligned with the needs of the
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community. We welcome comment both from Expat users, would-be users,
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and members of the XML community who have decided against using Expat
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for technical reasons directly related to Expat.</p>
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2002-09-04 23:13:05 -04:00
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<p>Discussion of this document should be directed to the <a href=
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"http://mail.libexpat.org/mailman-21/listinfo/" >expat-discuss</a>
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mailing list.</p>
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2002-09-04 11:47:40 -04:00
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<h3>Goals</h3>
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<p>We do <strong>not</strong> plan to alter the goals of the Expat
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project. We intend to continue to develop Expat to have the following
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qualities:</p>
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<ul>
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<li> Fast </li>
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<li> Conformant to XML 1.0 and Namespaces </li>
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<li> Easy to use from C </li>
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<li> Easy to wrap / bind for non-C languages </li>
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<li> Sufficient to build DOM and SAX on top of
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(any final specification for XML) </li>
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<li> Modest memory footprint </li>
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<li> Portable </li>
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</ul>
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<h3>Non-Goals</h3>
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<ul>
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<li> Parsing anything that isn't XML </li>
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<li> DOM (any level) </li>
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<li> SAX (any version) </li>
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<li> Data bindings </li>
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<li> Watching the kids </li>
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</ul>
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<h3>Historical Background</h3>
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<p>James Clark initially developed Expat, releasing three stable
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versions, identified as versions 1.0, 1.1, and 1.2. Clark Cooper
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created a forked version of Expat based on Expat 1.1, for use in the
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XML::Parser extension module for Perl.</p>
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<p>As James Clark's interests shifted, and his development moved to
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the Java environment, the authors of 3rd party language bindings found
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it increasingly difficult to integrate Expat with their languages, and
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other developers found it difficult to get fixes accepted into Expat
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and released. A small group of extension authors were gathered by
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Paul Prescod in the hope that Expat could be formed into a more
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readily usable library for both direct use in C-language applications
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and indirect use from other languages. This group was led by Clark
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Cooper and Fred Drake, and received sanction to take over maintenance
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of Expat from James Clark. The project is hosted on SourceForge.
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This group made their first release as Expat 1.95.0 in September
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2000.</p>
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<p>Since that time, incremental releases of Expat have been made on a
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sporadic schedule, improving functionality and portability with each
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release.</p>
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<h3>Expat Development Roadmap</h3>
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<p>Now that our goals and non-goals have been spelled out, let's take
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a look at how we should get there from where we are now. This will be
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broken down into two stages: near future activities and far future
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activities. In spite of the somewhat temporal labeling of these
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categories, please realize that no actual scheduling has been done,
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nor is that considered relevant at this time. Actual time to meet
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these goals is dependent on the availability of resources to work on
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Expat. Parallel development may also happen, depending on the
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specific interests of contributers.</p>
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<h4>Near Future Activity</h4>
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<p>The target of the current line of development will be to release Expat
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2.0. The intent is that once Expat 2.0 is released, most of the
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development activity for this line will be maintenance, and will be
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driven by user-provided problem reports. These are the goals for
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goals we have specific to the release of Expat 2.0:</p>
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<ul>
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<li> Stabilize the current API with some minor revisions to make error
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reporting more explicit to allow better reporting and diagnosis. </li>
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<li> Introduce a new feature-test macro, XML_MINIMAL, parallel to
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XML_DTD, XML_UNICODE, and XML_UNICODE_WCHAR_T. Defining the new
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feature when compiling Expat will cause functions that are not
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relevant to the rest of the feature macros. (For example, if
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XML_DTD is not set but XML_MINIMAL is, the functions that set
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handlers for DTD-related events won't be included at all.) This
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is intended to make it easier to use Expat in small-memory
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devices. </li>
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<li> API revisions will be made to improve the runtime discoverability of
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Expat capabilities. </li>
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<li> Improve portability and performance. </li>
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<li> Substantially improve regression tests. </li>
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<li> Improve documentation. </li>
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<li> Full support for 64-bit platforms. (There are some known decoding
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problems currently.) </li>
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</ul>
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<p>When we're confident that the minor API changes are "right", we'll
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finallize the API and release Expat 2.0. Should additional functions
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be required as evolutionary improvements, the minor version number
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will be incremented, but all existing functions will be maintained for
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backward compatibility. Releases that are strictly bug fixes will
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have the same minor version number and will gain a "micro" version
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number (sometimes called a "patch level").</p>
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<h4>Far Future Activity</h4>
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<p>Once Expat 2.0 has been released, it will be maintained on a CVS
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branch. The head of CVS will be used to develop Expat 3.0. The
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changes in Expat 3.0 will be more substantial and will include
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important API changes. At this time, we're looking at the following
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changes:</p>
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<dl>
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<dt> More powerful event API </dt>
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<dd>
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<p>The new API will be sufficiently detailed that a complete and
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detailed DOM structure can be built, including both internal and
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2002-09-04 13:06:06 -04:00
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external entity boundaries in parsed character data content,
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attribute value content, and entity values (such as found in
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internal entity declarations).</p>
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2002-09-04 11:47:40 -04:00
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<p>This API will of necessity be somewhat more complex than the
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current API, but we expect the current API can be implemented on top
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of the new API. For users for whom the Expat 2.0 API is
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sufficiently powerful, this API will remain available.</p>
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</dd>
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2002-09-04 13:25:37 -04:00
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<dt> Support for either pull or suspendable parsing </dt>
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<dd>
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2002-09-04 13:26:58 -04:00
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<p>The new API will need to support some way to interrupt processing
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without having to parse all XML text passed to the parser so far.
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This can be done by either using a pull-based model or a push-based
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model (similar to the current API) with the added ability to suspend
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parsing on request.</p>
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2002-09-04 13:25:37 -04:00
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<p>The specific API will depend on the model selected; either a
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pull-based model or an suspension model can support each other with
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little additional work, and the current push model can be built on
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top of either.</p>
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<p>The specific model and API will be discussed on the <a href=
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"http://mail.libexpat.org/mailman-21/listinfo/" >expat-discuss</a>
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mailing list.</p>
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</dt>
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2002-09-04 11:47:40 -04:00
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<dt> New encoding support </dt>
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<dd>
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<p>A new library may be added to the Expat package that provides a
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flexible architecture for defining new encodings, and provides a
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large range of common encodings. (It should be possible to develop
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this so that it supports both Expat 2.0 and Expat 3.0.)</p>
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<p>Another approach which will be considered will be to support
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Expat's requirements for decoders using one of the existing open
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source encoding support libraries that meets Expat's requirements
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for portability. Possible technical approaches would include
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implementing an adapter, and developing such an external library to
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include direct support for the kind of interface support Expat
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needs.</p>
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</dd>
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2002-09-05 16:18:45 -04:00
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<dt> <a href= "http://www.w3.org/TR/xml11/" >XML 1.1</a> (including <a
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href="http://www.w3.org/TR/xml-names11/" >Namespaces in XML
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1.1</a>), if it ever happens </dt>
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2002-09-04 11:47:40 -04:00
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<dd>
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<p>Well, we're hoping, but it's not time to code for this yet.</p>
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</dd>
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</dl>
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<p>Additional goals may be added during the development of Expat 3.0;
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it's just too early to tell.</p>
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</td>
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</tr>
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<td class="corner">
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<a href="http://sourceforge.net/">
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<img src="http://cvs.sourceforge.net/sourceforge_whitebg.gif"
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width="136" height="79" border="0" alt="SourceForge
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Logo" />
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</a>
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