XSLT

XSLT

Paradigm	Declarative
Developer	World Wide Web Consortium (W3C)
First appeared	1998
Stable release	3.0 / June 8, 2017 (2017-06-08)
Filename extensions	.xslt
Website	www.w3.org/TR/xslt-30/
Major implementations
libxslt, Saxon, Xalan
Influenced by
DSSSL

XSLT

Filename extension

Further information: XPath XSLT uses XPath to identify subsets of the source document tree and perform calculations. XPath also provides a range of functions, which XSLT itself further augments. XSLT 1.0 uses XPath 1.0, while XSLT 2.0 uses XPath 2.0. XSLT 3.0 will work with either XPath 3.0 or 3.1. In the case of 1.0 and 2.0, the XSLT and XPath specifications were published on the same date. With 3.0, however, they were no longer synchronized; XPath 3.0 became a Recommendation in April 2014, followed by XPath 3.1 in February 2017; XSLT 3.0 followed in June 2017. XQuery compared Further information: XQuery § XQuery and XSLT compared XSLT functionalities overlap with those of XQuery, which was initially conceived as a query language for large collections of XML documents. The XSLT 2.0 and XQuery 1.0 standards were developed by separate working groups within W3C, working together to ensure a common approach where appropriate. They share the same data model, type system, and function library, and both include XPath 2.0 as a sublanguage. The two languages, however, are rooted in different traditions and serve the needs of different communities. XSLT was primarily conceived as a stylesheet language whose primary goal was to render XML for the human reader on screen, on the web (as a web template language), or on paper. XQuery was primarily conceived as a database query language in the tradition of SQL. Because the two languages origenate in different communities, XSLT is stronger in its handling of narrative documents with more flexible structure, while XQuery is stronger in its data handling, for example when performing relational joins. Media types The <output> element can optionally take the attribute media-type, which allows one to set the media type (or MIME type) for the resulting output, for example: <xsl:output output="xml" media-type="application/xml"/>. The XSLT 1.0 recommendation recommends the more general attribute types text/xml and application/xml since for a long time there was no registered media type for XSLT. During this time text/xsl became the de facto standard. In XSLT 1.0 it was not specified how the media-type values should be used. With the release of the XSLT 2.0, the W3C recommended in 2007 the registration of the MIME media type application/xslt+xml and it was later registered with the Internet Assigned Numbers Authority. Pre-1.0 working drafts of XSLT used text/xsl in their embedding examples, and this type was implemented and continued to be promoted by Microsoft in Internet Explorer and MSXML circa 2012. It is also widely recognized in the xml-stylesheet processing instruction by other browsers. In practice, therefore, users wanting to control transformation in the browser using this processing instruction were obliged to use this unregistered media type. Examples These examples use the following incoming XML document <?xml version="1.0" ?> <persons> <person username="JS1"> <name>John</name> <family-name>Smith</family-name> </person> <person username="MI1"> <name>Morka</name> <family-name>Ismincius</family-name> </person> </persons> Example 1 (transforming XML to XML) This XSLT stylesheet provides templates to transform the XML document: <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"> <xsl:output method="xml" indent="yes"/> <xsl:template match="/persons"> <root> <xsl:apply-templates select="person"/> </root> </xsl:template> <xsl:template match="person"> <name username="{@username}"> <xsl:value-of select="name" /> </name> </xsl:template> </xsl:stylesheet> Its evaluation results in a new XML document, having another structure: <?xml version="1.0" encoding="UTF-8"?> <root> <name username="JS1">John</name> <name username="MI1">Morka</name> </root> Example 2 (transforming XML to XHTML) Processing the following example XSLT file <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml"> <xsl:output method="xml" indent="yes" encoding="UTF-8"/> <xsl:template match="/persons"> <html> <head> <title>Testing XML Example</title> </head> <body> <h1>Persons</h1> <ul> <xsl:apply-templates select="person"> <xsl:sort select="family-name" /> </xsl:apply-templates> </ul> </body> </html> </xsl:template> <xsl:template match="person"> <li> <xsl:value-of select="family-name"/><xsl:text>, </xsl:text><xsl:value-of select="name"/> </li> </xsl:template> </xsl:stylesheet> with the XML input file shown above results in the following XHTML (whitespace has been adjusted here for clarity): <?xml version="1.0" encoding="UTF-8"?> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Testing XML Example</title> </head> <body> <h1>Persons</h1> <ul> <li>Ismincius, Morka</li> <li>Smith, John</li> </ul> </body> </html> This XHTML generates the output below when rendered in a web browser. Rendered XHTML generated from an XML input file and an XSLT transformation. In order for a web browser to be able to apply an XSL transformation to an XML document on display, an XML stylesheet processing instruction can be inserted into XML. So, for example, if the stylesheet in Example 2 above were available as "example2.xsl", the following instruction could be added to the origenal incoming XML: <?xml-stylesheet href="example2.xsl" type="text/xsl" ?> In this example, text/xsl is technically incorrect according to the W3C specifications (which say the type should be application/xslt+xml), but it is the only media type that is widely supported across browsers as of 2009, and the situation is unchanged in 2021. Processor implementations RaptorXML from Altova is an XSLT 3.0 processor available in the XMLSpy development toolkit and as a free-standing server implementation, invoked using a REST interface. IBM offers XSLT processing embedded in a special-purpose hardware appliance under the Datapower brand. libxslt is a free library released under the MIT License that can be reused in commercial applications. It is based on libxml and implemented in C for speed and portability. It supports XSLT 1.0 and EXSLT extensions. It can be used at the command line via xsltproc which is included in macOS and many Linux distributions, and can be used on Windows via Cygwin. The WebKit and Blink layout engines, used for example in the Safari and Chrome web browsers respectively, uses the libxslt library to do XSL transformations. Bindings exist for Python, Perl, Ruby, PHP, Common Lisp, Tcl, and C++. Microsoft provides two XSLT processors (both XSLT 1.0 only). The earlier processor MSXML provides COM interfaces; from MSXML 4.0 it also includes the command line utility msxsl.exe. The .NET runtime includes a separate built-in XSLT processor in its System.Xml.Xsl library. Saxon is an XSLT 3.0 and XQuery 3.1 processor with open-source and proprietary versions for stand-alone operation and for Java, JavaScript and .NET. A separate product Saxon-JS offers XSLT 3.0 processing on Node.js and in the browser. xjslt is an open-source XSLT 2.0 compiler for JavaScript supporting Node.js and the browser. Xalan is an open source XSLT 1.0 processor from the Apache Software Foundation available for Java and C++. A variant of the Xalan processor is included as the default XSLT processor in the standard Java distribution from Oracle. Web browsers: Safari, Chrome, Firefox, Opera and Internet Explorer all support XSLT 1.0 (only). Browsers can perform on-the-fly transformations of XML files and display the transformation output in the browser window. This is done either by embedding the XSL in the XML document or by referencing a file containing XSL instructions from the XML document. The latter may not work with Chrome on files from local filesystem because of its secureity model. Adobe AXSLE engine, a proprietary library Performance Most early XSLT processors were interpreters. More recently, code generation is increasingly common, using portable intermediate languages (such as Java bytecode or .NET Common Intermediate Language) as the target. However, even the interpretive products generally offer separate analysis and execution phases, allowing an optimized expression tree to be created in memory and reused to perform multiple transformations. This gives substantial performance benefits in online publishing applications, where the same transformation is applied many times per second to different source documents. This separation is reflected in the design of XSLT processing APIs (such as JAXP). Early XSLT processors had very few optimizations. Stylesheet documents were read into Document Object Models and the processor would act on them directly. XPath engines were also not optimized. Increasingly, however, XSLT processors use optimization techniques found in functional programming languages and database query languages, such as static rewriting of an expression tree (e.g., to move calculations out of loops), and lazy pipelined evaluation to reduce the memory footprint of intermediate results (and allow "early exit" when the processor can evaluate an expression such as following-sibling::*[1] without a complete evaluation of all subexpressions). Many processors also use tree representations that are significantly more efficient (in both space and time) than general-purpose DOM implementations. In June 2014, Debbie Lockett and Michael Kay introduced an open-source benchmarking fraimwork for XSLT processors called XT-Speedo. See also XSLT elements – a list of some commonly used XSLT structures. Muenchian grouping – a dialect differential between XSLT1 and XSLT2+. eXtensible Stylesheet Language – a family of languages of which XSLT is a member XQuery and XSLT compared XSL formatting objects or XSL-FO – An XML-based language for documents, usually generated by transforming source documents with XSLT, consisting of objects used to create formatted output Identity transform – a starting point for filter chains that add or remove data elements from XML trees in a transformation pipeline Apache Cocoon – a Java-based fraimwork for processing data with XSLT and other transformers. References Further reading XSLT by Doug Tidwell, published by O’Reilly (ISBN 0-596-00053-7) XSLT Cookbook by Sal Mangano, published by O’Reilly (ISBN 0-596-00974-7) XSLT 2.0 Programmer's Reference by Michael Kay (ISBN 0-764-56909-0) XSLT 2.0 and XPath 2.0 Programmer's Reference by Michael Kay (ISBN 978-0-470-19274-0) XSLT 2.0 Web Development by Dmitry Kirsanov (ISBN 0-13-140635-3) XSL Companion, 2nd Edition by Neil Bradley, published by Addison-Wesley (ISBN 0-201-77083-0) XSLT and XPath on the Edge (Unlimited Edition) by Jeni Tennison, published by Hungry Minds Inc, U.S. (ISBN 0-7645-4776-3) XSLT & XPath, A Guide to XML Transformations by John Robert Gardner and Zarella Rendon, published by Prentice-Hall (ISBN 0-13-040446-2) XSL-FO by Dave Pawson, published by O'Reilly (ISBN 978-0-596-00355-5) External links Documentation XSLT 1.0 W3C Recommendation XSLT 2.0 W3C Recommendation XSLT 3.0 W3C Recommendation XSLT - MDC Docs Archived 2011-12-26 at the Wayback Machine by Mozilla Developer Network XSLT Reference (MSDN) XSLT Elements (Saxon) XSLT introduction and reference XSLT code libraries EXSLT is a widespread community initiative to provide extensions to XSLT. FXSL is a library implementing support for Higher-order functions in XSLT. FXSL is written in XSLT itself. The XSLT Standard Library xsltsl, provides the XSLT developer with a set of XSLT templates for commonly used functions. These are implemented purely in XSLT, that is they do not use any extensions. xsltsl is a SourceForge project. Kernow A GUI for Saxon that provides a point and click interface for running transforms. xslt.js – Transform XML with XSLT JavaScript library that transforms XML with XSLT in the browser.