IBM Version 5 manual Xalan model of operation

3.2 Xalan

Xalan is an XSLT processor for transforming XML documents into HTML, text, or other XML document types. It implements the W3C Recommendations for XSL Transformations (XSLT) and the XML Path Language (XPath). It provides a standard API for performing XML Transformations. It builds on SAX2, DOM Level2, and the XML parser API in Java API for XML Parsing 1.0 (JAXP). It may be configured to work with any XML parser, such as Xerces, that implements JAXP. It can process Stream, SAX or DOM input, and output to a Stream, SAX or DOM.

The diagram in Figure 3-1 shows a high level model of operation. A transformation expressed in XSLT describes the rules for transforming a source tree into a result tree. A term tree represents the structure of an XML document, whether it is a DOM tree, or a series of parse events coming from a SAX2 ContentHandler. The transformation is achieved by associating patterns with templates. A pattern is matched against elements in the source tree. A template is instantiated to create part of the result tree. The result tree is separate from the source tree. The structure of the result tree can be completely different from the structure of the source tree. In constructing the result tree, elements from the source tree can be filtered and reordered.

Source	XSLT	Result
XML
	Engine	XML
	XSL
	Style
	Sheet

Figure 3-1 Xalan model of operation

The primary interface for Xalan for external usage is javax.xml.transform. These interfaces define a standard and powerful interface to perform tree-based transformations. These interfaces have no dependencies on SAX or the DOM standard as shown in Figure 3-2. It achieves this by defining source and result interfaces, which a user can use to define instances of whatever input and output desired, whether SAX, DOM, or stream.

Chapter 3. Processing XML 57