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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/REC-html40/loose.dtd">
<html>
<head>
<title>XT</title>
</head>
<body>
<h1>XT</h1>
<h2>Version 19990725</h2>
<p>Copyright (c) 1998, 1999 James Clark</p>
<p>See the file <a href="copying.txt">copying.txt</a> for copying
permission.</p>
<p>XT is an implementation in Java of <a
href="http://www.w3.org/TR/1999/WD-xslt-19990709">XSL
Transformations</a>. This version of XT implements the
WD-xslt-19990709 version of XSLT. Stylesheets written for earlier
versions of the XSLT WD must be converted before they can be used with
this version of XT.</p>
<p>This should be considered a beta release.</p>
<h2><a name="usage">Usage</a></h2>
<p>To use XT, you need:</p>
<ul>
<li><a href="ftp://ftp.jclark.com/pub/xml/xt.zip">the XT distribution</a></li>
<li>an XML parser in Java that supports <a
href="http://www.megginson.com/SAX/">SAX</a>, such as <a
href="http://www.jclark.com/xml/xp/index.html">XP</a>; you should
choose a SAX parser that provides <code>Locator</code> information,
otherwise you won't get any line numbers in error messages</li>
</ul>
<p>Put <code>xt.jar</code> in your <code>CLASSPATH</code>, together
with whatever is needed for your XML parser, and <code>sax.jar</code>
if that isn't included with your XML parser. Then use the
command:</p>
<pre>
java -Dcom.jclark.xsl.sax.parser=<var>your-sax-driver</var> com.jclark.xsl.sax.Driver <var>source</var> <var>stylesheet</var> <var>result</var>
</pre>
<p>To find a SAX parser, XT first uses the value of the system
property <code>com.jclark.xsl.sax.parser</code>; if this is not set it
uses the value of the system property <code>org.xml.sax.parser</code>;
if this is not set it uses the class
<code>com.jclark.xml.sax.CommentDriver</code> (This subclasses the
normal XP SAX driver to provide support for comments; it is present
only in XP version 0.5 or later; if you have an earlier version of XP
use <code>-Dcom.jclark.xsl.sax.parser=com.jclark.xml.sax.Driver</code>
instead.)</p>
<p>Alternatively under Windows you can use <a
href="ftp://ftp.jclark.com/pub/xml/xt-win32.zip">XT packaged as a
Win32 executable</a>. This includes XP and SAX. To use this, you will
need to have the <a
href="http://www.microsoft.com/java/vm/dl_vm32.htm">Microsoft Java
VM</a> installed (this is included with IE). Run this with the
command:</p>
<pre>
xt <var>source</var> <var>stylesheet</var> <var>result</var>
</pre>
<h2>XT API</h2>
<p>The public interface to XT is
<code>com.jclark.xsl.sax.XSLProcessor</code> which is implemented by
<code>com.jclark.xsl.sax.XSLProcessorImpl</code>.</p>
<h2>Limitations</h2>
<p>The following features of the XSLT WD are not yet implemented:</p>
<ul>
<li>the <code>substring</code> function</li>
<li>the <code>string-length</code> function</li>
<li>attribute sets</li>
<li>the <code>preceding</code> axis</li>
<li>the <code>namespace</code> axis</li>
<li>the <code>xsl:locale</code> element and the optional third
argument on the <code>format-number()</code> function</li>
<li>multiple source documents (the <code>document()</code> function)</li>
<li>keys (the <code>xsl:key</code> element, and the <code>key()</code>
function)</li>
<li>the <code>xsl:message</code> element</li>
<li>the element extension mechanism</li>
<li>the <code>unparsed-entity-uri</code> function</li>
<li>the <code>result-encoding</code> attribute on
<code>xsl:stylesheet</code></li>
<li>the <code>result-version</code> attribute on
<code>xsl:stylesheet</code></li>
</ul>
<p>Error reporting is rather haphazard. XT does not attempt to
validate stylesheets. When it detects an error, it either silently
recovers from it, or gives a fatal error. Forwards-compatible
processing is not yet implemented.</p>
<p>Not much effort has yet been devoted to optimizing performance.
The implementation of some features is known to be slow (notably
<code>xsl:number</code>).</p>
<h2><a name="extension">Extension Functions</a></h2>
<p>A call to a function <code><var>ns</var>:<var>foo</var></code>
where <code><var>ns</var></code> is bound to a namespace of the form
<code>http://www.jclark.com/xt/java/<var>className</var></code> is
treated as a call of the static method <code><var>foo</var></code> of
the class with fully-qualified name
<code><var>className</var></code>. (XT does not currently make use of
the <code>xsl:functions</code> element.) Hyphens in method names are
removed with the character following the hyphen being upper-cased.
Overloading based on number of parameters is supported; overloading
based on parameter types is not. A non-static method is treated like
a static method with the <code>this</code> object as an additional
first argument. A constructor is treated like a static method named
<code>new</code>. Extension functions can return objects of arbitrary
types which can then be passed as arguments to other extension
functions or stored in variables.</p>
<p>For example, the following</p>
<pre><xsl:stylesheet
xmlns:xsl="http://www.w3.org/XSL/Transform/1.0"
xmlns:date="http://www.jclark.com/xt/java/java.util.Date"
xmlns="http://www.w3.org/TR/REC-html40"
result-ns="">
<xsl:template match="/">
<html>
<xsl:if test="function-available('date:to-string') and function-available('date:new')">
<p><xsl:value-of select="date:to-string(date:new())"/></p>
</xsl:if>
</html>
</xsl:template>
</xsl:stylesheet></pre>
<p>will print out the current date.</p>
<p>Types are mapped between XSLT and Java as follows:</p>
<table border="1">
<tr><th>XSLT type</th><th align="left">Java type</th></tr>
<tr><td>string</td><td><code>java.lang.String</code></td>
<tr><td>number</td><td><code>double</code></td></tr>
<tr><td>boolean</td><td><code>boolean</code></td></tr>
<tr><td>node-set</td><td><code>com.jclark.xsl.om.NodeIterator</code></td></tr>
<tr><td>result tree fragment</td><td><code>com.jclark.xsl.sax.ResultTreeFragment</code></td></tr>
</table>
<p>On return from an extension function, an object of type
<code>com.jclark.xsl.om.Node</code> is also allowed and will be
treated node-set; also any numeric type is allowed an will be
converted to a number.</p>
<p>The <code>demo</code> directory has a couple of examples.</p>
<h2><a name="nonxml">Non-XML output</a></h2>
<p>The <code>result-ns</code> attribute can be used to get non-XML
output. A result namespace of
<code>http://www.w3.org/TR/REC-html40</code> will make XT produce
output that conforms to the HTML 4.0 Recommendation. To use this the
<code>xsl:stylesheet</code> element should look like this:</p>
<pre><xsl:stylesheet
xmlns:xsl="http://www.w3.org/XSL/Transform/1.0"
xmlns="http://www.w3.org/TR/REC-html40"
result-ns="">
</xsl:stylesheet></pre>
<p>The result namespace can also use a <code>java:</code> URI. This
should identify a class that implements the
<code>org.xml.sax.DocumentHandler</code> and
<code>com.jclark.xsl.sax.OutputStreamConverter</code> interfaces.</p>
<p>The <code>com.jclark.xsl.sax.NXMLOutputHandler</code> is one such
class, which is included in XT. This supports a result namespace
which is described by the following DTD:</p>
<pre><!ELEMENT nxml (escape*, (control|data)*)>
<!ATTLIST nxml encoding NMTOKEN #IMPLIED>
<!ELEMENT escape (#PCDATA|char)*>
<!ATTLIST escape char CDATA #REQUIRED>
<!ELEMENT control (#PCDATA|char|data|control)*>
<!ELEMENT data (#PCDATA|data|control)*>
<!ELEMENT char EMPTY>
<!ATTLIST char number NMTOKEN #REQUIRED></pre>
<p>The <code>nxml</code> element is the root element; the
<code>encoding</code> attribute is the <a
href="http://java.sun.com/products/jdk/1.1/docs/guide/intl/encoding.doc.html"
>name of an encoding supported by your Java VM</a> that will be used
to encode characters as bytes.</p>
<p>The <code>data</code> element contains data. Within a
<code>data</code> element control characters get escaped. The
<code>escape</code> element specifies how a particular control
character gets escaped.</p>
<p>The <code>control</code> element contains control information.
Within a <code>control</code> element, all characters are output
directly without escaping.</p>
<p>The <code>char</code> element allows the output of a character that
is not allowed by XML (such as control-L).</p>
<p>For example, the following stylesheet</p>
<pre><xsl:stylesheet
xmlns:xsl="http://www.w3.org/XSL/Transform/1.0"
xmlns="java:com.jclark.xsl.sax.NXMLOutputHandler"
result-ns="">
<xsl:template match="/">
<nxml>
<escape char="\">\\</escape>
<data>&amp;&lt;&gt;\</data>
<control>&amp;&lt;&gt;\</control>
</nxml>
</xsl:template>
</xsl:stylesheet></pre>
<p>will output</p>
<pre>&<>\\&<>\</pre>
<h2><a name="bug">Reporting Bugs</a></h2>
<p>Please report bugs to me. <strong>When reporting bugs please be
sure to include both a complete stylesheet and complete source
document that illustrate the bug</strong>.</p>
<address>
<a href="mailto:jjc@jclark.com">James Clark</a>
</address>
</body>
</html>
|
