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| |
| <UL> |
| <LI><A href="#functionality">Functionality</A></LI> |
| <LI><A href="#overview">Namespace overview</A></LI> |
| <LI><A href="#NSA">The DOM & namespaces</A></LI> |
| <LI><A href="#NSB">Namespaces in the XSL stylesheet</A></LI> |
| <LI><A href="#NSC">Namespaces in the output document</A></LI> |
| </UL> |
| <A name="functionality"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Functionality</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif"> |
| |
| <P>Namespaces are used when an XML documents has elements have the same |
| name, but are from different contexts, and thus have different meanings |
| and interpretations. For instance, a <CODE><FONT face="courier, monospaced"><TITLE></FONT></CODE> element can |
| be a HTML title element in one part of the XML document, while it in other |
| parts of the document the <CODE><FONT face="courier, monospaced"><TITLE></FONT></CODE> element is used for |
| encapsulating the title of a play or a book. This sort of confusion is |
| very common when reading XML source from multiple documents, but can also |
| occur within a single document.</P> |
| |
| <P>Namespaces have three very important properties: a name, a prefix (an |
| alias for its name) and a scope. Namespaces are declared as attributes of |
| almost any node in an XML document. The declaration looks like this:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| <element xmlns:prefix="http://some.site/spec">....</element> |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>The <CODE><FONT face="courier, monospaced">"xmlns"</FONT></CODE> tells that this is a namespace declaration. The |
| scope of the namespace declaration is the element in which it is defined |
| and all the children of that element.The prefix is the local alias we use |
| for referencing the namespace, and the URL (it can be anything, really) is |
| the name/definition of the namespace. Note that even though the namespace |
| definition is normally an URL, it does not have to point to anything. It |
| is recommended that it points to a page that describes the elements in the |
| namespace, but it does not have to. The prefix can be just about anything |
| - or nothing (in which case it is the default namespace). Any prefix, |
| including the empty prefix for the default namespace, can be redefined to |
| refer to a different namespace at any time in an XML document. This is |
| more likely to happen to the default namespace than any other prefix. Here |
| is an example of this:</P> |
| |
| <A name="xml_sample_1"><!--anchor--></A> |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| <?xml version="1.0"?> |
| |
| <employees xmlns:postal="http://postal.ie/spec-1.0" |
| xmlns:email="http://www.w3c.org/some-spec-3.2"> |
| <employee> |
| <name>Bob Worker</name> |
| <postal:address> |
| <postal:street>Nassau Street</postal:street> |
| <postal:city>Dublin 3</postal:city> |
| <postal:country>Ireland</postal:country> |
| </postal:address> |
| <email:address>bob.worker@hisjob.ie</email:address> |
| </employee> |
| </employees> |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>This short document has two namespace declarations, one with the prefix |
| <CODE><FONT face="courier, monospaced">"postal"</FONT></CODE> and another with the prefix <CODE><FONT face="courier, monospaced">"email"</FONT></CODE>. The |
| prefixes are used to distinguish between elements for e-mail addresses and |
| regular postal addresses. In addition to these two namespaces there is also |
| an initial (unnamed) default namespace being used for the |
| <CODE><FONT face="courier, monospaced"><name></FONT></CODE> and <CODE><FONT face="courier, monospaced"><employee></FONT></CODE> tags. The scope of the |
| default namespace is in this case the whole document, while the scope of |
| the other two declared namespaces is the <CODE><FONT face="courier, monospaced"><employees></FONT></CODE> |
| element and its children.</P> |
| |
| <P>By changing the default namespace we could have made the document a |
| little bit simpler and more readable:</P> |
| |
| <A name="xml_sample_2"><!--anchor--></A> |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| <?xml version="1.0"?> |
| |
| <employees xmlns:email="http://www.w3c.org/some-spec-3.2"> |
| <employee> |
| <name>Bob Worker</name> |
| <address xmlns="http://postal.ie/spec-1.0"> |
| <street>Nassau Street</street> |
| <city>Dublin 3</city> |
| <country>Ireland</country> |
| </address> |
| <email:address>bob.worker@hisjob.ie</email:address> |
| </employee> |
| </employees> |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>The default namespace is redefined for the <CODE><FONT face="courier, monospaced"><address></FONT></CODE> node |
| and its children, so there is no need to specify the street as |
| <CODE><FONT face="courier, monospaced"><postal:street></FONT></CODE> - just plain <CODE><FONT face="courier, monospaced"><street></FONT></CODE> is |
| sufficient. Note that this also applies to the <CODE><FONT face="courier, monospaced"><address></FONT></CODE> |
| where the namespace is first defined. This is in effect a redefinition of |
| the default namespace.</P> |
| </FONT></TD></TR></TABLE><BR><A name="overview"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Namespace overview</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif"> |
| |
| <P>Namespaces will have to be handled in three separate parts of the XSLT |
| compiler:</P> |
| |
| <A name="all_namespaces"><!--anchor--></A> |
| <P><IMG align="right" alt="all_namespaces.gif" border="0" hspace="4" src="images/all_namespaces.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 1: Namespace handlers in the XSLTC</I></P> |
| |
| <P>The most obvious is the namespaces in the source XML document |
| (marked <A href="#NSA">"NS A"</A> in figure 1). These namespaces will be |
| handled by our DOM implementation class. The source XSL stylesheet also |
| has its own set of namespaces (<A href="NSB.html">"NS B"</A>) - one of which |
| is the XSL namespace. These namespaces will be handled at run-time and |
| whatever information that is needed to process there should be compiled |
| into the translet. There is also a set of namespaces that will be used in |
| the resulting document (<A href="NSC.html">"NS C"</A>). This is an |
| intersection of the first two. The output document should not contain any |
| more namespace declarations than necessary.</P> |
| |
| </FONT></TD></TR></TABLE><BR><A name="NSA"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>The DOM & namespaces</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif"> |
| <UL> |
| <LI><A href="#dom-namespace">DOM node types and namespace types</A></LI> |
| <LI><A href="#assign">Assigning namespace types to DOM nodes</A></LI> |
| </UL> |
| <A name="dom-namespace"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>DOM node types and namespace types</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1"> |
| |
| <P>Refer to the XSLTC <A href="xsltc_runtime.html">runtime |
| environment design</A> document for a description of node types before |
| proceeding. In short, each node in the our DOM implementation is |
| represented by a simple integer. By using this integer as an index into an |
| array called <CODE><FONT face="courier, monospaced">_type[]</FONT></CODE> we can find the type of the node.</P> |
| |
| <P>The type of the node is an integer representing the type of element the |
| node is. All elements <CODE><FONT face="courier, monospaced"><bob></FONT></CODE> will be given the same type, |
| all text nodes will be given the same type, and so on. By using the node |
| type as an index an array called <CODE><FONT face="courier, monospaced">_namesArray[]</FONT></CODE> we can find the |
| name of the element type - in this case "bob". This code fragment shows |
| how you can, with our current implementation, find the name of a node:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| int node = iterator.getNext(); // get next node |
| int type = _type[node]; // get node type |
| String name = _namesArray[type]; // get node name |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>We want to keep the one-type-per-node arrangement, since that lets us |
| produce fairly efficient code. One type in the DOM maps to one type in |
| the compiled translet. What we could do to represent the namespace for |
| each node in the DOM is to add a <CODE><FONT face="courier, monospaced">_namespaceType[]</FONT></CODE> array that holds |
| namespace types. Each node type maps to a namespace type, and each |
| namespace type maps to a namespace name (and a prefix with a limited |
| scope):</P> |
| |
| <A name="type_mappings"><!--anchor--></A> |
| <P><IMG align="right" alt="type_mappings.gif" border="0" hspace="4" src="images/type_mappings.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 2: Mapping between node types/names, namespace types/names</I></P> |
| |
| <P>This code fragment shows how we could get the namespace name for a node:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| int node = iterator.getNext(); // get next node |
| int type = _type[node]; // get node type |
| int nstype = _namespace[type]; // get namespace type |
| String name = _namesArray[type]; // get node element name |
| String namespace = _nsNamesArray[nstype]; // get node namespace name |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>Note that namespace prefixes are not included here. Namespace prefixes |
| are local to the XML document and will be expanded to the full namespace |
| names when the nodes are put into the DOM. This, however, is not a trivial |
| matter.</P> |
| </FONT></TD></TR></TABLE><BR><A name="assign"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Assigning namespace types to DOM nodes</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1"> |
| |
| <P>We cannot simply have a single namespace prefix array similar to the |
| <CODE><FONT face="courier, monospaced">_namespaceArray[]</FONT></CODE> array for mapping a namespace type to a single |
| prefix. This because prefixes can refer to different namespaces depending |
| on where in the document the prefixes are being used. In our last example's |
| <A href="xml_sample_2.html">XML fragment</A> the empty prefix <CODE><FONT face="courier, monospaced">""</FONT></CODE> |
| initially referred to the default namespace (the one with no name - just |
| like a Clint Eastwood character). Later on in the document the empty |
| prefix is changed to refer to a namespace called |
| <CODE><FONT face="courier, monospaced">"http://postal.ie/spec-1.0"</FONT></CODE>.</P> |
| |
| <P>Namespace prefixes are only relevant at the time when the XML document |
| is parsed and the DOM is built. Once we have the DOM completed we only need |
| a table that maps each node type to a namespace type, and another array of |
| all the names of the different namespaces. So what we want to end up with |
| is something like this:</P> |
| |
| <P><IMG align="right" alt="dom_namespace1.gif" border="0" hspace="4" src="images/dom_namespace1.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 3: Each namespace references in the DOM gets one entry</I></P> |
| |
| <P>The namespace table has one entry for each namespace, nomatter how many |
| prefixes were used ro reference this namespace in the DOM. To build this |
| array we need a temporary data structure used by the DOM builder. This |
| structure is a hashtable - where the various prefixes are used for the |
| hash values. The contents of each entry in the table will be a small stack |
| where previous meanings of each prefix will be stored:</P> |
| |
| <P><IMG align="right" alt="dom_namespace2.gif" border="0" hspace="4" src="images/dom_namespace2.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 4: Temporary data structure used by the DOM builder</I></P> |
| |
| <P>When the first node is encountered we define a new namespace |
| <CODE><FONT face="courier, monospaced">"foo"</FONT></CODE> and assign this namespace type/index 1 (the default |
| namespace <CODE><FONT face="courier, monospaced">""</FONT></CODE> has index 0). At the same time we use the prefix |
| <CODE><FONT face="courier, monospaced">"A"</FONT></CODE> for a lookup in the hashtable. This gives us |
| an integer stack used for the prefix <CODE><FONT face="courier, monospaced">"A"</FONT></CODE>. We push the namespace |
| type 1 on this stack. From now on, until <CODE><FONT face="courier, monospaced">"A"</FONT></CODE> is pop'ed off this |
| stack, the prefix <CODE><FONT face="courier, monospaced">"A"</FONT></CODE> will map to namespace type 1, which |
| represents the namespace URI <CODE><FONT face="courier, monospaced">"foo"</FONT></CODE>.</P> |
| |
| <P>We then encounter the next node with a new namespace definition with |
| the same namespace prefix, we create a new namespace <CODE><FONT face="courier, monospaced">"bar"</FONT></CODE> and |
| we put that in the namespace table under type 2. Again we use the prefix |
| <CODE><FONT face="courier, monospaced">"A"</FONT></CODE> as an entry into the namespace prefix table and we get the |
| same integer stack. We now push namespace type 2 on the stack, so that |
| namespace prefix <CODE><FONT face="courier, monospaced">"A"</FONT></CODE> maps to namespace URI <CODE><FONT face="courier, monospaced">"bar"</FONT></CODE>. When |
| we have traversed this node's children we need to pop the integer off the |
| stack, so when we're back at the first node the prefix <CODE><FONT face="courier, monospaced">"A"</FONT></CODE> again |
| will point to namespace type 0, which maps to <CODE><FONT face="courier, monospaced">"foo"</FONT></CODE>. To keep |
| track of what nodes had what namespace declarations, we use a namespace |
| declaration stack:</P> |
| |
| <P><IMG align="right" alt="dom_namespace3.gif" border="0" hspace="4" src="images/dom_namespace3.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 5: Namespace declaration stack</I></P> |
| |
| <P>Every namespace declaration is pushed on the namespace declaration |
| stack. This stack holds the node index for where the namespace was |
| declared, and a reference to the prefix stack for this declaration. |
| The <CODE><FONT face="courier, monospaced">endElement()</FONT></CODE> method of the DOMBuilder class will need to |
| remove namespace declaration for the node that is closed. This is done |
| by first checking the namespace declaration stack for any namespaces |
| declared by this node. If any declarations are found these are un-declared |
| by poping the namespace prefixes off the respective prefix stack(s), and |
| then poping the entry/entries for this node off the namespace declaration |
| stack.</P> |
| |
| <P>The <CODE><FONT face="courier, monospaced">endDocument()</FONT></CODE> method will build an array that contains |
| all namespaces used in the source XML document - <CODE><FONT face="courier, monospaced">_nsNamesArray[]</FONT></CODE> |
| - which holds the URIs of all refered namespaces. This method also builds |
| an array that maps all DOM node types to namespace types. This two arrays |
| are accessed through two new methods in the DOM interface:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| public String getNamespaceName(int node); |
| public int getNamespaceType(int node); |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| </FONT></TD></TR></TABLE><BR></FONT></TD></TR></TABLE><BR><A name="NSB"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Namespaces in the XSL stylesheet</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif"> |
| <UL> |
| <LI><A href="#store-access">Storing and accessing namespace information</A></LI> |
| <LI><A href="#mapdom-stylesheet">Mapping DOM namespaces to stylesheet namespaces</A></LI> |
| <LI><A href="#wildcards">Wildcards and namespaces</A></LI> |
| </UL> |
| <A name="store-access"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Storing and accessing namespace information</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1"> |
| <P>The SymbolTable class has three datastructures that are used to hold |
| namespace information:</P> |
| |
| <UL> |
| <LI> |
| First there is the <CODE><FONT face="courier, monospaced">_namespaces[]</FONT></CODE> Hashtable that maps the names |
| of in-scope namespace to their respective prefixes. Each key in the |
| Hashtable object has a stack. A new prefix is pushed on the stack for |
| each new declaration of a namespace. |
| </LI> |
| <LI> |
| Then there is the <CODE><FONT face="courier, monospaced">_prefixes[]</FONT></CODE> Hashtable. This has the reverse |
| function of the <CODE><FONT face="courier, monospaced">_namespaces[]</FONT></CODE> Hashtable - it maps from |
| prefixes to namespaces. |
| </LI> |
| <LI> |
| There is also a hashtable that is used for implementing the |
| <CODE><FONT face="courier, monospaced"><xsl:namespace-alias></FONT></CODE> element. The keys in this |
| hashtable is taken from the <CODE><FONT face="courier, monospaced">stylesheet-prefix</FONT></CODE> attribute of |
| this element, and the resulting prefix (from the <CODE><FONT face="courier, monospaced">result-prefix</FONT></CODE> |
| attribute) is used as the value for each key. |
| </LI> |
| </UL> |
| |
| <P>The SymbolTable class offers 4 methods for accessing these data |
| structures:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| public void pushNamespace(String prefix, String uri); |
| public void popNamespace(String prefix); |
| public String lookupPrefix(String uri); |
| public String lookupNamespace(String prefix); |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>These methods are wrapped by two methods in the Parser class (a Parser |
| object alwas has a SymbolTable object):</P> |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| // This method pushes all namespaces declared within a single element |
| public void pushNamespaces(ElementEx element); |
| // This method pops all namespaces declared within a single element |
| public void popNamespaces(ElementEx element); |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>The translet class has, just like the DOM, a <CODE><FONT face="courier, monospaced">namesArray[]</FONT></CODE> |
| structure for holding the expanded QNames of all accessed elements. The |
| compiled translet fills this array in its constructor. When the translet |
| has built the DOM (a DOMImpl object), it passes the DOM to the a DOM |
| adapter (a DOMAdapter object) together with the names array. The DOM |
| adapter then maps the translet's types to the DOM's types.</P> |
| </FONT></TD></TR></TABLE><BR><A name="mapdom-stylesheet"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Mapping DOM namespaces and stylesheet namespaces</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1"> |
| |
| <P>Each entry in the DOM's <CODE><FONT face="courier, monospaced">_namesArray[]</FONT></CODE> is expanded to contain |
| the full QName, so that instead of containing <CODE><FONT face="courier, monospaced">prefix:localname</FONT></CODE> it |
| will now contain <CODE><FONT face="courier, monospaced">namespace-uri:localname</FONT></CODE>. In this way the expanded |
| QName in the translet will match the exanded QName in the DOM. This assures |
| matches on full QNames, but does not do much for <CODE><FONT face="courier, monospaced">match="A:*"</FONT></CODE> type |
| XPath patterns. This is where our main challenge lies.</P> |
| </FONT></TD></TR></TABLE><BR><A name="wildcards"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Wildcards and namespaces</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1"> |
| |
| <P>The original implementation of the XSLTC runtime environment would |
| only allow matches on "<CODE><FONT face="courier, monospaced">*</FONT></CODE>" and "<CODE><FONT face="courier, monospaced">@*</FONT></CODE>" patterns. This was |
| achieved by mapping all elements that could not be mapped to a translet |
| type to 3 (DOM.ELEMENT type), and similarly all unknown attributes to |
| type 4 (DOM.ATTRIBUTE type). The main <CODE><FONT face="courier, monospaced">switch()</FONT></CODE> statement in |
| <CODE><FONT face="courier, monospaced">applyTemplates()</FONT></CODE> would then have a separate "<CODE><FONT face="courier, monospaced">case()</FONT></CODE>" |
| for each of these. (Under each <CODE><FONT face="courier, monospaced">case()</FONT></CODE> you might have to check |
| for the node's parents in case you were matching on "<CODE><FONT face="courier, monospaced">path/*</FONT></CODE>"-type |
| patterns.) This figure shows how that was done:</P> |
| |
| <A name="match_namespace1"><!--anchor--></A> |
| <P><IMG align="right" alt="match_namespace1.gif" border="0" hspace="4" src="images/match_namespace1.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 6: Previous pattern matching</I></P> |
| |
| <P>The "Node test" box here represents the "<CODE><FONT face="courier, monospaced">switch()</FONT></CODE>" statement. |
| The "Node parent test" box represent each "<CODE><FONT face="courier, monospaced">case:</FONT></CODE>" for that |
| <CODE><FONT face="courier, monospaced">switch()</FONT></CODE> statement. There is one <CODE><FONT face="courier, monospaced">case:</FONT></CODE> for each know |
| translet node type. For each node type we have to check for any parent |
| patterns - for instance, for the pattern "<CODE><FONT face="courier, monospaced">/foo/bar/baz</FONT></CODE>", we will |
| get a match with <CODE><FONT face="courier, monospaced">case "baz"</FONT></CODE>, and we have to check that the parent |
| node is "<CODE><FONT face="courier, monospaced">bar</FONT></CODE>" and that the grandparent is "<CODE><FONT face="courier, monospaced">foo</FONT></CODE>" before |
| we can say that we have a hit. The "Element parent test" is the test that |
| is done all DOM nodes that do not directly match any translet types. This |
| is the test for "<CODE><FONT face="courier, monospaced">*</FONT></CODE>" or "<CODE><FONT face="courier, monospaced">foo/*</FONT></CODE>". Similarly we have a |
| "<CODE><FONT face="courier, monospaced">case:</FONT></CODE>" for match on attributes ("<CODE><FONT face="courier, monospaced">@*</FONT></CODE>").</P> |
| |
| <P>What we now want to achieve is to insert a check for patterns on the |
| format "<CODE><FONT face="courier, monospaced">ns:*</FONT></CODE>", "<CODE><FONT face="courier, monospaced">foo/ns:*</FONT></CODE>" or "<CODE><FONT face="courier, monospaced">ns:@*</FONT></CODE>", which |
| this figure illustrates:</P> |
| |
| <A name="match_namespace2"><!--anchor--></A> |
| <P><IMG align="right" alt="match_namespace2.gif" border="0" hspace="4" src="images/match_namespace2.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 7: Pattern matching with namespace tests</I></P> |
| |
| |
| <P>Each node in the DOM needs a namespace type as well as the QName type. |
| With this type we can match wildcard rules to any specific namespace. |
| So after any checks have been done on the whole QName of a node (the type), |
| we can match on the namespace type of the node. The main dispatch |
| <CODE><FONT face="courier, monospaced">switch()</FONT></CODE> in <CODE><FONT face="courier, monospaced">applyTemplates()</FONT></CODE> must be changed from this:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| public void applyTemplates(DOM dom, NodeIterator iterator, |
| TransletOutputHandler handler) { |
| |
| // Get next node from iterator |
| while ((node = iterator.next()) != END) { |
| // Get internal node type |
| final int type = DOM.getType(node); |
| switch(type) { |
| case DOM.ROOT: // Match on "/" pattern |
| handleRootNode(); |
| break; |
| case DOM.TEXT: // Handle text nodes |
| handleText(); |
| break; |
| case DOM.ELEMENT: // Match on "*" pattern |
| handleWildcardElement(); |
| break; |
| case DOM.ATTRIBUTE: // Handle on "@*" pattern |
| handleWildcardElement(); |
| break; |
| case nodeType1: // Handle 1st known element type |
| compiledCodeForType1(); |
| break; |
| : |
| : |
| : |
| case nodeTypeN: // Handle nth known element type |
| compiledCodeForTypeN(); |
| break; |
| default: |
| NodeIterator newIterator = DOM.getChildren(node); |
| applyTemplates(DOM, newIterator, handler); |
| break; |
| } |
| } |
| return; |
| } |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>To something like this:</P> |
| |
| <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE> |
| public void applyTemplates(DOM dom, NodeIterator iterator, |
| TransletOutputHandler handler) { |
| |
| // Get next node from iterator |
| while ((node = iterator.next()) != END) { |
| |
| // First run check on node type |
| final int type = DOM.getType(node); |
| switch(type) { |
| case DOM.ROOT: // Match on "/" pattern |
| handleRootNode(); |
| continue; |
| case DOM.TEXT: // Handle text nodes |
| handleText(); |
| continue; |
| case DOM.ELEMENT: // Not handled here!!! |
| break; |
| case DOM.ATTRIBUTE: // Not handled here!!! |
| break; |
| case nodeType1: // Handle 1st known element type |
| if (compiledCodeForType1() == match) continue; |
| break; |
| : |
| : |
| : |
| case nodeTypeN: // Handle nth known element type |
| if (compiledCodeForTypeN() == match) continue; |
| break; |
| default: |
| break; |
| } |
| |
| // Then run check on namespace type |
| final int namespace = DOM.getNamespace(type); |
| switch(namespace) { |
| case 0: // Handle nodes matching 1st known namespace |
| if (handleThisNamespace() == match) continue; |
| break; |
| case 1: // Handle nodes matching 2nd known namespace |
| if (handleOtherNamespace() == match) continue; |
| break; |
| } |
| |
| // Finally check on element/attribute wildcard |
| if (type == DOM.ELEMENT) { |
| if (handleWildcardElement() == match) |
| continue; |
| else { |
| // The default action for elements |
| NodeIterator newIterator = DOM.getChildren(node); |
| applyTemplates(DOM, newIterator, handler); |
| } |
| } |
| else if (type == DOM.ATTRIBUTE) { |
| handleWildcardAttribute(); |
| continue; |
| } |
| } |
| } |
| </PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV> |
| |
| <P>First note that the default action (iterate on children) does not hold for |
| attributes, since attribute nodes do not have children. Then note that the way |
| the three levels of tests are ordered is consistent with the way patterns |
| should be prioritised:</P> |
| |
| <UL> |
| |
| <LI><B>Match on element/attribute types:</B></LI> |
| <UL> |
| <LI><CODE><FONT face="courier, monospaced">match="/"</FONT></CODE> - match on the root node</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="B"</FONT></CODE> - match on any B element</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="A/B"</FONT></CODE> - match on B elements with A parent</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="A | B"</FONT></CODE> - match on B or A element</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="foo:B"</FONT></CODE> - match on B element within "foo" namespace</LI> |
| </UL> |
| <LI><B>Match on namespace:</B></LI> |
| <UL> |
| <LI><CODE><FONT face="courier, monospaced">match="foo:*"</FONT></CODE> - match on any element within "foo" namespace</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="foo:@*"</FONT></CODE> - match on any attribute within "foo" namespace</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="A/foo:*"</FONT></CODE> - match on any element within "foo" namespace with A parent</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="A/foo:@*"</FONT></CODE> - match on any attribute within "foo" namespace with A parent</LI> |
| </UL> |
| |
| <LI><B>Match on wildcard:</B> </LI> |
| <UL> |
| <LI><CODE><FONT face="courier, monospaced">match="*"</FONT></CODE> - match on any element</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="@*"</FONT></CODE> - match on any attribute</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="A/*"</FONT></CODE> - match on any element with A parent</LI> |
| <LI><CODE><FONT face="courier, monospaced">match="A/@*"</FONT></CODE> - match on any attribute with A parent</LI> |
| </UL> |
| |
| </UL> |
| |
| </FONT></TD></TR></TABLE><BR></FONT></TD></TR></TABLE><BR><A name="NSC"><!--anchor--></A> |
| <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Namespaces in the output document</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10"> </TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif"> |
| |
| <P>These are the categories of namespaces that end up in the output |
| document:</P> |
| |
| <UL> |
| <LI> |
| Namespaces used in literal elements/attributes in the stylesheet. These |
| namespaces should be declared <B>once</B> before use in the output |
| document. These elements are copied to the output document independent |
| of namespaces in the input XML document. However, the namespaces can |
| be declared using the same prefix, such that a namespace used by a |
| literal result element can overshadow a namespace from the DOM. |
| </LI> |
| <LI> |
| Namespaces from elements in the stylesheet that match elements in the |
| DOM. No namespaces from the DOM should be copied to the output document |
| unless they are actually referenced in the stylesheet. No namespaces |
| from the stylesheet should be copied to the output document unless the |
| elements in which they are references match elements in the DOM. |
| </LI> |
| </UL> |
| |
| <A name="output_namespaces1"><!--anchor--></A> |
| <P><IMG align="right" alt="output_namespaces1.gif" border="0" hspace="4" src="images/output_namespaces1.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 8: Namespace declaration in the output document</I></P> |
| |
| <P>Any literal element that ends up in the output document must declare all |
| namespaces that were declared in the <CODE><FONT face="courier, monospaced"><xsl:stylesheet<</FONT></CODE> |
| element. Exceptions are namespaces that are listed in this element's |
| <CODE><FONT face="courier, monospaced">exclude-result-prefixes</FONT></CODE> or <CODE><FONT face="courier, monospaced">extension-element-prefixes</FONT></CODE> |
| attributes. These namespaces should only be declared if they are referenced |
| in the output.</P> |
| |
| <P>Literal elements should only declare namespaces when necessary. A |
| literal element should only declare a namespace in the case where it |
| references a namespace using prefix that is not in scope for this |
| namespace. The output handler will take care of this problem. All namespace |
| declarations are put in the output document using the output handler's |
| <CODE><FONT face="courier, monospaced">declarenamespace()</FONT></CODE> method. This method will monitor all namespace |
| declarations and make sure that no unnecessary declarations are output. |
| The datastructures used for this are similar to those used to track |
| namespaces in the XSL stylesheet:</P> |
| |
| <A name="output_namespaces2"><!--anchor--></A> |
| <P><IMG align="right" alt="output_namespaces2.gif" border="0" hspace="4" src="images/output_namespaces2.gif" vspace="4"><BR clear="all"></P> |
| <P><I>Figure 9: Handling Namespace declarations in the output document</I></P> |
| |
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| Copyright © 2004 The Apache Software Foundation. |
| All Rights Reserved. |
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