Extensible Stylesheet Language (XSL)

Specifications and Working Drafts - Learning XSL - Software - FAQ - History

XSL is a language for expressing stylesheets. It consists of two parts:

• XSL Transformations (XSLT): a language for transforming XML documents
• An XML vocabulary for specifying formatting semantics

An XSL stylesheet specifies the presentation of a class of XML documents by describing how an instance of the class is transformed into an XML document that uses the formatting vocabulary. For background information on style sheets, see the Web style sheets resource page. XSL is developed by the W3C XSL Working Group (members only) whose charter is to develop the next version of XSL.

News

• 001012 Sablotron is now available as an extension to PHP4. It claims to be a very fast server-side XSLT processor for Win32.
• 001011 Xalan-C++ v1.0 XSLT processor released.
• 001010 Chapter 15 of the XML Bible, XSL Formatting Objects, is available online.
• 001010 French translation of the XSLT1.0 Recommendation available. See also our translations page.
• 001010 Kevin Jones has set up an XSLT benchmark page.
• 001010 The new release of Unicorn XSLT Processor, Professional Edition version 1.02.16 is available (runs on Windows NT 4.0).
• 001005 XPath 1.0 Errata list updated.
• 001005 The Mozilla XSLT project (aka Transformiix) now has its own project page.
• 001004 PassiveTeX version 1.1 released.
• 000930 Microsoft release a September MSXML Beta. It claims to be a "complete implementation" of XSLT and XPath.
• 000914 PassiveTeX version 1.0, 2000/09/14 released.
• 000914 New release of xslide: XSL mode for emacs (Revision 0.2 Beta 1).
• 000825 XSL Transformations Requirements Version 1.1 is posted on W3C site.
• 000724 Announcement of XSLTC, an XSLT compiler. It takes as input an XSLT stylesheet, and generates C++ code that is expected to have the same behaviour as the source stylesheet.
• 000703 The W3C XSL Working Group is rechartered with a new charter.
• 000630 Ginger Alliance announce release 0.4 of Sablotron, which is now available under MPL/GPL license.
• 000626 Sun Microsystems announce a free XSLT compiler
• 000529 Sebastian Rahtz announces a new release of PassiveTeX, an implementation of the March 2000 draft.
• 000327 XSL enters Last Call with a new Working Draft
• 000323 LotusXSL 1.0.0 is available from alphaWorks
• 000321 Xalan-J 1.0.0 Gold Release posted to xml.apache.org/dist
• 000315 MSXML Parser V3.0 released
• 000301 New XSL working draft published
• 000126 Microsoft releases XSL to XSLT Converter 1.0. The xsl-xslt-converter.xslt style sheet updates Microsoft Internet Explorer 5 XSL style sheets to XSLT-compliant style sheets
• 000112 New XSL working draft published

Older News.

Specifications and Working Drafts

The latest versions of the XSL specification are:

• Extensible Stylesheet Language (XSL) - W3C Working Draft
• XSL Transformations (XSLT) Specification - W3C Recommendation
• XML Path Language (XPath) - W3C Recommendation

Some of them have been translated from English and are available in other languages.

Learning XSL

XSL Frequently Asked Questions maintained by Dave Pawson. Not a tutorial, but a very good source for learning XSL.

XSL Concepts and Practical Use by P. Grosso and N. Walsh was presented at the XML Europe 2000 Conference in Paris, France.

A short XSL tutorial is provided by XML101.

XSLT Programmer's Reference by Mike Kay is probably the first book dedicated to XSLT and XPath.

Training material is available for sale from Crane Softwrights Ltd: Practical Transformation Using XSLT and XPath. It covers the transformation part of XSL (XSLT), including XPath.

Chapter 14 of the XML Bible is dedicated to XSLT, Chapter 15 is dedicated to XSL-FO. Both are available online.

Miloslav Nic has provided code samples demonstrating basic and advanced concepts in his online resource. He has also published a complete XSLT Reference.

A nice introduction to XSLT, the transformation part of XSL, can be found in the Microsoft XSL document.

A good way to learn is by example, so have a look at the XSL Slidemaker from the Koala Group at INRIA/Sophia, which takes an XML file of slides and processes them with XSL.

• The XSL Tutorial given by Norm Walsh and Paul Grosso of Arbortext at XML 98
• A short XSL Tutorial from Henry Thompson, given at SGML UK in October 1997
• A tutorial in iX magazine (in German)

Other XSL Resources include

• XSLINFO, from James Tauber.
• XSL Resources at Oasis
• the XSL Jumpstart from jeremie.com
• the XSL section on finetuning.com
• Koala XSL resources.

XSL-enabled software

XSLT Processors

• Unicorn XSLT transformation engine, freely available for Windows.
• Sun's XSLT Compiler creates a Java program that performs the transformation instructions described by a XSLT file.
• XSLTC is an XSLT compiler. It takes as input an XSLT stylesheet, and generates C++ code that is expected to have the same behaviour as the source stylesheet.
• 4XSLT is an XML transformation processor written in Python that implements the XSLT transform language.
• The InDelv browser implements XSL stylesheets, including the FO part for direct display. It also implements XLink.
• XSL is integrated into the Microsoft XML processor which is part of Internet Explorer 5. It transforms XML into HTML, which is then displayed using CSS; it does not implement FOs. See conformance notes.
• iXSLT from Infoteria is a XSLT processor written in C++
• LotusXSL is a complete implementation of the W3C Recommendations for XSL Transformations (XSLT) and the XML Path Language (XPath)
• Transformiix is an standalone XSLT processor in C++, and can also be used within Mozilla.
• Resin is a servlet/JSP engine with integrated XPath and XSLT support.
• Sablotron is an attempt to develop a fast, compact and portable XSLT processor written in C++
• Sablot XSLT is an extension of Sablotron for PHP4/Win 32.
• Saxon is a collection of tools for processing XML documents. It includes a complete implementation of the XSLT 1.0 and XPath 1.0 Recommendations, as well as a Jave library.
• Xalan-Java and Xalan-C++ are a implementations of the W3C recommendations XSLT and XPath. They are provided by the Apache XML Project.
• The XML Parser for Java v2 from Oracle incorporates support for XSL Transformations (XSLT)
• XMLwriter is an XML editor that supports XSL, so you can transform the content and style of your XML documents.
• XT from James Clark is a free Java-based implementation of XSLT.

XSL-FO processors

• Unicorn Formatting Objects (UFO) is freely available and runs on Windows NT 4.0 and Windows 95. It implements the substantial subset of the Extensible Stylesheet Language (XSL) Version 1.0 specification (W3C Working Draft 27 March 2000)
• FOP is a XSL FO to PDF converter developed by James Tauber at the Apache Software FoundationXE
• Passive TeX is a library of TeX macros which provides a rapid development environment for experimenting with XSL FO.
• REXP is an early implementation of a Formatting Objects engine based on FOP. It generates PDF files. It's an open source.
• XEP (formerly known as FOP2PDF) from RenderX is a program for converting XSL FO documents to PDF.

XSL-Enabled Authoring Tools

• xslide: an emacs mode for XSL stylesheets.
• eXcelon Stylus combines tools to create XSL stylesheets in a visual editing environment.
• The IBM XSL Editor application allows a user to import, create, and save XSL style sheets and XML source documents

Older Implementations

Frequently Asked Questions

How is XSL different from CSS?

XSL uses a XML notation, CSS uses its own. In CSS, the formatting object tree is almost the same as the source tree, and inheritance of formatting properties is on the source tree. In XSL, the formatting object tree can be radically different from the source tree, and inheritance of formatting properties is on the formatting object tree.

Aside from these technical differences, mature implementations of CSS1 and (parts of) CSS2 are available, whilst XSL is currently too new to have mature browser and content-authoring support.

Will XSL replace CSS?

No. They are likely to co-exist since they meet different needs. XSL is intended for complex formatting where the content of the document might be displayed in multiple places; for example the text of a heading might also appear in a dynamically generated table of contents. CSS is intended for dynamic formatting of online documents for multiple media; its strictly declarative nature limits its capabilities but also makes it efficient and easy to generate and modify in the content-generation workflow. So they are two different tools; for some tasks, CSS is the appropriate choice and for some tasks, XSL. They can also be used together - use XSL on the server to condense or customize some XML data into a simpler XML document, then use CSS to style it on the client.

How is XSL different from DSSSL? From DSSSL-O?

DSSSL is an International Standard style sheet language. It is particularly used for formatting of print documents. DSSSL-O is a profile of DSSSL which removes some functionality and adds capabilities to make it more suited for online documentation. XSL draws on DSSSL and the DSSSL-O work and continues the trend towards a Web-oriented style sheet language by integrating experience with CSS.

Will XSL replace DSSSL?

DSSSL has capabilities that XSL does not, and continues in use in the print publishing industry. Experience with XSL might be used in a future revision of DSSSL, but it is too early to say.

So, CSS is for HTML and XSL is for XML?

No, CSS can be used with HTML and also with XML, provided that the XML document has a reasonably linear structure that can be displayed without extensive manipulation. See the CSS2 Recommendation for details.

XSL is targeted at XML, in particular highly-structured, data-rich documents that require extensive formatting.

Should I render all my XML documents to HTML on the server?

Unless you are very careful to retain semantics, no. XSL can be used server-side and client-side. The XSL Submission has two classes of output: DSSSL-style flow objects and HTML tags. Unfortunately, the combination of server-side processing and HTML tag output can result in completely inaccessible, hard to search, hard to index presentational HTML (the sort that is a mass of FONT and BR tags, spacer gifs - you know, the sort of single-shot presentational mess that style sheets were designed to avoid).

The trouble is that by "rendering" to HTML, all that remains of your carefully crafted XML semantics are the presentational aspects - block element, this font, that weight - which makes it hard to generate decent HTML.

Technical: how do I do X, Y or Z in XSL?

First, have a look at D. Pawson's excellent XSL FAQ. If you don't find an answer, check the XSL mailing list at mulberrytech.com.

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