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diff --git a/libjava/classpath/gnu/xml/dom/package.html b/libjava/classpath/gnu/xml/dom/package.html deleted file mode 100644 index fbc864a..0000000 --- a/libjava/classpath/gnu/xml/dom/package.html +++ /dev/null @@ -1,273 +0,0 @@ -<html> -<body> - -<p> -This is a Free Software DOM Level 3 implementation, supporting these features: -<ul> -<li>"XML"</li> -<li>"Events"</li> -<li>"MutationEvents"</li> -<li>"HTMLEvents" (won't generate them though)</li> -<li>"UIEvents" (also won't generate them)</li> -<li>"USER-Events" (a conformant extension)</li> -<li>"Traversal" (optional)</li> -<li>"XPath"</li> -<li>"LS" and "LS-Async"</li> -</ul> -It is intended to be a reasonable base both for -experimentation and supporting additional DOM modules as clean layers. -</p> - -<p> -Note that while DOM does not specify its behavior in the -face of concurrent access, this implementation does. -Specifically: -<ul> -<li>If only one thread at a time accesses a Document, -of if several threads cooperate for read-only access, -then no concurrency conflicts will occur.</li> -<li>If several threads mutate a given document -(or send events using it) at the same time, -there is currently no guarantee that -they won't interfere with each other.</li> -</ul> -</p> - -<h3>Design Goals</h3> - -<p> -A number of DOM implementations are available in Java, including -commercial ones from Sun, IBM, Oracle, and DataChannel as well as -noncommercial ones from Docuverse, OpenXML, and Silfide. Why have -another? Some of the goals of this version: -</p> - -<ul> -<li>Advanced DOM support. This was the first generally available -implementation of DOM Level 2 in Java, and one of the first Level 3 -and XPath implementations.</li> - -<li> Free Software. This one is distributed under the GPL (with -"library exception") so it can be used with a different class of -application.</li> - -<li>Second implementation syndrome. I can do it simpler this time -around ... and heck, writing it only takes a bit over a day once you -know your way around.</li> - -<li>Sanity check the then-current Last Call DOM draft. Best to find -bugs early, when they're relatively fixable. Yes, bugs were found.</li> - -<li>Modularity. Most of the implementations mentioned above are part -of huge packages; take all (including bugs, of which some have far -too many), or take nothing. I prefer a menu approach, when possible. -This code is standalone, not beholden to any particular parser or XSL -or XPath code.</li> - -<li>OK, I'm a hacker, I like to write code.</li> -</ul> - -<p> -This also works with the GNU Compiler for Java (GCJ). GCJ promises -to be quite the environment for programming Java, both directly and from -C++ using the new CNI interfaces (which really use C++, unlike JNI). </p> - - -<h3>Open Issues</h3> - -<p>At this writing:</p> -<ul> -<li>See below for some restrictions on the mutation event -support ... some events aren't reported (and likely won't be).</li> - -<li>More testing and conformance work is needed.</li> - -<li>We need an XML Schema validator (actually we need validation in the DOM -full stop).</li> -</ul> - -<p> -I ran a profiler a few times and remove some of the performance hotspots, -but it's not tuned. Reporting mutation events, in particular, is -rather costly -- it started at about a 40% penalty for appendNode calls, -I've got it down around 12%, but it'll be hard to shrink it much further. -The overall code size is relatively small, though you may want to be rid of -many of the unused DOM interface classes (HTML, CSS, and so on). -</p> - - -<h2><a name="features">Features of this Package</a></h2> - -<p> Starting with DOM Level 2, you can really see that DOM is constructed -as a bunch of optional modules around a core of either XML or HTML -functionality. Different implementations will support different optional -modules. This implementation provides a set of features that should be -useful if you're not depending on the HTML functionality (lots of convenience -functions that mostly don't buy much except API surface area) and user -interface support. That is, browsers will want more -- but what they -need should be cleanly layered over what's already here. </p> - -<h3> Core Feature Set: "XML" </h3> - -<p> This DOM implementation supports the "XML" feature set, which basically -gets you four things over the bare core (which you're officially not supposed -to implement except in conjunction with the "XML" or "HTML" feature). In -order of decreasing utility, those four things are: </p> <ol> - - <li> ProcessingInstruction nodes. These are probably the most - valuable thing. Handy little buggers, in part because all the APIs - you need to use them are provided, and they're designed to let you - escape XML document structure rules in controlled ways.</li> - - <li> CDATASection nodes. These are of of limited utility since CDATA - is just text that prints funny. These are of use to some sorts of - applications, though I encourage folk to not use them. </li> - - <li> DocumentType nodes, and associated Notation and Entity nodes. - These appear to be useless. Briefly, these "Type" nodes expose no - typing information. They're only really usable to expose some lexical - structure that almost every application needs to ignore. (XML editors - might like to see them, but they need true typing information much more.) - I strongly encourage people not to use these. </li> - - <li> EntityReference nodes can show up. These are actively annoying, - since they add an extra level of hierarchy, are the cause of most of - the complexity in attribute values, and their contents are immutable. - Avoid these.</li> - - </ol> - -<h3> Optional Feature Sets: "Events", and friends </h3> - -<p> Events may be one of the more interesting new features in Level 2. -This package provides the core feature set and exposes mutation events. -No gooey events though; if you want that, write a layered implementation! </p> - -<p> Three mutation events aren't currently generated:</p> <ul> - - <li> <em>DOMSubtreeModified</em> is poorly specified. Think of this - as generating one such event around the time of finalization, which - is a fully conformant implementation. This implementation is exactly - as useful as that one. </li> - - <li> <em>DOMNodeRemovedFromDocument</em> and - <em>DOMNodeInsertedIntoDocument</em> are supposed to get sent to - every node in a subtree that gets removed or inserted (respectively). - This can be <em>extremely costly</em>, and the removal and insertion - processing is already significantly slower due to event reporting. - It's much easier, and more efficient, to have a listener higher in the - tree watch removal and insertion events through the bubbling or capture - mechanisms, than it is to watch for these two events.</li> - - </ul> - -<p> In addition, certain kinds of attribute modification aren't reported. -A fix is known, but it couldn't report the previous value of the attribute. -More work could fix all of this (as well as reduce the generally high cost -of childful attributes), but that's not been done yet. </p> - -<p> Also, note that it is a <em>Bad Thing™</em> to have the listener -for a mutation event change the ancestry for the target of that event. -Or to prevent mutation events from bubbling to where they're needed. -Just don't do those, OK? </p> - -<p> As an experimental feature (named "USER-Events"), you can provide -your own "user" events. Just name them anything starting with "USER-" -and you're set. Dispatch them through, bubbling, capturing, or what -ever takes your fancy. One important thing you can't currently do is -pass any data (like an object) with those events. Maybe later there -will be a "UserEvent" interface letting you get some substantial use -out of this mechanism even if you're not "inside" of a DOM package.</p> - -<p> You can create and send HTML events. Ditto UIEvents. Since DOM -doesn't require a UI, it's the UI's job to send them; perhaps that's -part of your application. </p> - -<p><em>This package may be built without the ability to report mutation -events, gaining a significant speedup in DOM construction time. However, -if that is done then certain other features -- notably node iterators -and getElementsByTagname -- will not be available.</em> - - -<h3> Optional Feature: "Traversal" </h3> - -<p> Each DOM node has all you need to walk to everything connected -to that node. Lightweight, efficient utilities are easily layered on -top of just the core APIs. </p> - -<p> Traversal APIs are an optional part of DOM Level 2, providing -a not-so-lightweight way to walk over DOM trees, if your application -didn't already have such utilities for use with data represented via -DOM. Implementing this helped debug the (optional) event and mutation -event subsystems, so it's provided here. </p> - -<p> At this writing, the "TreeWalker" interface isn't implemented. </p> - - - -<h2><a name='avoid'>DOM Functionality to Avoid</a></h2> - -<p> For what appear to be a combination of historical and "committee -logic" reasons, DOM has a number of <em>features which I strongly advise -you to avoid using</em> in your library and application code. These -include the following types of DOM nodes; see the documentation for the -implementation class for more information: <ul> - - <li> CDATASection - (<a href='DomCDATA.html'>DomCDATA</a> class) - ... use normal Text nodes instead, so you don't have to make - every algorithm recognize multiple types of character data - - <li> DocumentType - (<a href='DomDoctype.html'>DomDocType</a> class) - ... if this held actual typing information, it might be useful - - <li> Entity - (<a href='DomEntity.html'>DomEntity</a> class) - ... neither parsed nor unparsed entities work well in DOM; it - won't even tell you which attributes identify unparsed entities - - <li> EntityReference - (<a href='DomEntityReference.html'>DomEntityReference</a> class) - ... permitted implementation variances are extreme, all children - are readonly, and these can interact poorly with namespaces - - <li> Notation - (<a href='DomNotation.html'>DomNotation</a> class) - ... only really usable with unparsed entities (which aren't well - supported; see above) or perhaps with PIs after the DTD, not with - NOTATION attributes - - </ul> - -<p> If you really need to use unparsed entities or notations, use SAX; -it offers better support for all DTD-related functionality. -It also exposes actual -document typing information (such as element content models).</p> - -<p> Also, when accessing attribute values, use methods that provide their -values as single strings, rather than those which expose value substructure -(Text and EntityReference nodes). (See the <a href='DomAttr.html'>DomAttr</a> -documentation for more information.) </p> - -<p> Note that many of these features were provided as partial support for -editor functionality (including the incomplete DTD access). Full editor -functionality requires access to potentially malformed lexical structure, -at the level of unparsed tokens and below. Access at such levels is so -complex that using it in non-editor applications sacrifices all the -benefits of XML; editor aplications need extremely specialized APIs. </p> - -<p> (This isn't a slam against DTDs, note; only against the broken support -for them in DOM. Even despite inclusion of some dubious SGML legacy features -such as notations and unparsed entities, -and the ongoing proliferation of alternative schema and validation tools, -DTDs are still the most widely adopted tool -to constrain XML document structure. -Alternative schemes generally focus on data transfer style -applications; open document architectures comparable to -DocBook 4.0 don't yet exist in the schema world. -Feel free to use DTDs; just don't expect DOM to help you.) </p> - -</body> -</html> - |