XSL

XSL stands for Extensible Stylesheet Language, a W3C specification family for expressing stylesheets and transformations of XML documents. The XSL family includes XSLT (Extensible Stylesheet Language Transformations), XSL-FO (Formatting Objects), and XPath, the language used to select nodes in an XML document during processing. XSLT is a transformation language that takes an XML input and produces a result tree in another XML language, HTML, or plain text. It uses templates that match nodes with XPath patterns; the processor applies templates and builds the output. XPath expressions navigate and compute values, conditions, and node sets.

XSL-FO defines a formatting vocabulary for paged presentation. An XSL-FO document describes how content should be laid out and paginated; it is typically rendered by an FO processor (e.g., Apache FOP) into PDF, PostScript, or other formats. A common pipeline is to transform source XML into XSL-FO with XSLT, then render with an FO processor to produce formatted output.

The XSL specification family was published by W3C in the late 1990s, with XSLT 1.0 and XSL-FO 1.0 as early recommendations, followed by XSLT 2.0/3.0 and XSL-FO 1.1. Modern implementations exist in multiple engines (Saxon, Xalan, Altova, Apache FOP). XSL is widely used for data presentation, report generation, and web publishing where structured XML must be transformed or formatted for display or print.