Extensible Stylesheet Language (XSL)

Extensible Stylesheet Language (XSL)

XSL is a language for expressing stylesheets. As such, XSL is about visual control. It can be used to
define exact text and picture placement in ways that HTML never could. Used in conjunction with XML, it
can theoretically be used to produce a single document in exactly the same format, whether a viewer
reads it on a computer monitor or on paper. Unlike Cascading Style Sheets, which are used to format
HTML pages, 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. In this schema, the content would be formatted based on which class of
information it appears as in each instance. Therefore, XSL should be used with XML in highly structured,
data-rich documents that require extensive formatting.
XSL consists of three parts: XSL Transformations (XSLT), the XML Path Language (XPath), and XSL
Formatting Objects:
l Extensible Stylesheet Language for Transformations (XSLT)-A language for transforming
XML documents. It allows for the changing of one XML document into another using XSL. XSLT
functions as a language in both the markup and the programming aspect since it can transform an
XML structure into either another XML structure, such as HTML, or into any variety of other textbased
formats, such as SQL. It can be used to create the display output of a Web page, but
XSLT's real advantage is that it can change the underlying structures of Web data instead of
simply the representations of those structures. XSLT is expected to eventually become one of the
primary programming languages for communications between systems.
l The XML Path Language (XPath)A query language for addressing parts of an XML document,
designed to be used by both XSLT and XML Pointer. XPath offers a basic syntax for selecting
subsets of nodes within a document and makes possible the retrieval of collections of elements by
specifying a directory-like path, as well as conditions placed on that path. XPath is critical for
XSLT and DOM.
l XSL Formatting Objects
The XML vocabulary for formatting semantics. An XSL stylesheet
specifies presentation by describing how an instance of each class of information is transformed
into an XML document using the formatting vocabulary.
Used together, these three protocols provide a highly scalable language for transforming unstructured
XML content into documents that have the same look and feel.

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