7.1 The Standards

The terms XSL and XSLT, while similar, do not refer to the same W3C specification. XSL, the Extensible Stylesheet Language itself, is simply a language for expressing stylesheets. A stylesheet is a document that controls the presentation of an XML document of a given type. XSL can be thought of as analogous to Cascading Style Sheets (CSS); in fact, XSL shares most of its properties with CSS2, although they have different syntaxes.

XSLT, the XSL Transformation language, is a subset of XSL that was originally designed to perform transformations of XML elements into complex styles, such as nested tables and indexes. XSLT is designed to be usable independent of XSL; however, its use is constrained by its design as a transformation language for the sorts of tasks required by XSL.

Despite the differences, you'll often see the acronyms XSL and XSLT used interchangeably. Unless the speaker is describing complete formatting systems, odds are good that XSL is probably actually a mis-cited reference to XSLT. To add to the confusion, Microsoft has chosen to call the .NET XSLT namespace System.Xml.Xsl.

XSL-FO, or XSL Formatting Objects, provides additional, more complex formatting for XML content. However, Microsoft does not implement any specific XSL-FO functionality in .NET, so it is outside the scope of this chapter. If you're interested in learning about XSL-FO, you should look into one of the available books about it, such as XSL-FO (O'Reilly) or Definitive XSL-FO (Prentice Hall).