Xalan-C++ (named after a rare musical instrument) implements the W3C Recommendation 16 November 1999 XSL Transformations (XSLT) Version 1.0 and the XML Path Language (XPath) Version 1.0. XSLT is the first part of the XSL stylesheet language for XML. It includes the XSL Transformation vocabulary and XPath, a language for addressing parts of XML documents. For links to background materials, discussion groups, frequently asked questions, and tutorials on XSLT, see Getting up to speed with XSLT.

XSL also includes a vocabulary for formatting documents, which is still under design and is not part of Xalan-C++. For more information, see W3C XSL Working Draft and the Apache XML FOP (Formatting Objects Project).

You use the XSLT language to compose XSL stylesheets. An XSL stylesheet contains instructions for transforming XML documents from one document type to another document type (XML, HTML, or other). In structural terms, an XSL stylesheet specifies the transformation of one tree of nodes (the XML input) into another tree of nodes (the output or transformation result).

The XSL stylesheet may generate and refer to cascading style sheets (CSS) as part of its output.

In the following example, the foo.xsl stylesheet is used to transform foo.xml into foo.out:

foo.xml:

	<?xml version="1.0"?> <doc>Hello</doc>

foo.xsl:

	<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl="https://www.w3.org/1999/XSL/Transform" version="1.0"> <xsl:template match="doc"> <out><xsl:value-of select="."/></out> </xsl:template> </xsl:stylesheet>

foo.out:

	<out>Hello</out>

• With a few minor exceptions, Xalan-C++ fully implements the W3C Recommendation 16 November 1999 XSL Transformations (XSLT) Version 1.0.
  
  For a list of the XSLT features that Xalan-C++ does not yet implement, see Xalan-C++ to-do tasks.
  
  
• Xalan-C++ incorporates the XML Path Language (XPath) Version 1.0.
  
  
• Xalan-C++ uses Xerces-C++ to parse XML documents and XSL stylesheets.
  
  The input may appear in the form of a file or URL, a stream, or a DOM. Xalan-C++ performs the transformations specified in the XSL stylesheet and produces a file, a stream, or a DOM as you specify when you set up the transformation.
  
  
• Along with a complete API for performing transformations in your C++ applications, Xalan-C++ provides a command line utility for convenient file-to-file transformations.
  
  
• Xalan-C++ supports C++ extension functions

For instructions and some suggestions about how to get started using Xalan-C++, see Getting Started.

If you are still working through the details of the XSLT spec (the W3C 1.0 Recommendation), you may want to consult one or more of the following:

• Elliotte Rusty Harold's Chapter 14 of the XML Bible: XSL Transformations (the online version is more current than the version in the printed book)
  
  
• Crane Softwright's Free preview of Practical Transformation Using XSLT and XPath
  
  
• The Mulberry XSL-List -- Open Forum on XSL (of interest to XSL users at all levels)
  
  
• Dave Pawson's XSL Frequently Asked Questions
  
  
• Objects by Design's Transforming XMI to HTML (oriented towards XMI, "an XML-based, stream representation of a UML model," but also covers "generic" XML transformations)
  
  
• Nic Miloslav's XSL Tutorial
  
  
• OASIS (the Organization for the Advancement of Structured Information Standards): Extensible Stylesheet Language (XSL) by Robin Cover
  
  
• Donald Ball's A Guide to XML and XSL for Designers
  
  
• Michael Kay's XSLT Programmer's Reference, Wrox Press, April 2000

When you come across other useful introductory or background materials, please email Don Leslie, so he can add them to this list.

XSLT Namespace

The XML namespace for XSLT. An XML namespace is a collection of element and attribute names, identified by a Unique Resource Identifier (URI), which often takes the form of a URL, but is really just a unique string, not a pointer to a web page. The XSLT namespace URI is https://www.w3.org/1999/XSL/Transform. In each XSLT stylesheet, you must declare this namespace in the stylesheet element tag and bind it to a local prefix. Like the XSLT specification, we always use xsl as the XSLT namespace prefix in our descriptions and examples, although you are free to bind any prefix to this namespace.

XSL Instruction

Any tag associated with the XSLT namespace.

Template

An element, usually with child elements, that specifies a "rule" or set of instructions to perform when a particular kind of node is encountered in the source tree.

XSL Template Instruction

Any tag that occurs inside an xsl:template element and is associated with the XSLT namespace.

Source Tree

The XML tree input to the XSL process.

Result Tree

The tree that is output by the XSL process.

Stylesheet Tree

The stylesheet tree produced from the XSL file.

Match Pattern

The part of a template that defines the kind(s) of nodes to which the template applies.

For more definitions of XSLT terminology, see Dave Pawson's XSLT Terminology Clarification and the Glossary in Michael Kay's XSLT Programmer's Reference.