2 XSL Transformation

2.1 Tree Construction

The Tree Construction is described in "XSL Transformations" [XSLT]. The data model in XSLT is capable of representing either an XML 1.0 document (conforming to [XML] and [XML Names]) or an XML 1.1 document (conforming to [XML 1.1] and [XML Names 1.1]), and it makes no distinction between the two. In principle, therefore, XSL 1.1 can be used with either of these XML versions; the only differences arise outside the boundary of the transformation proper, while creating the data model from textual XML (parsing).

The provisions in "XSL Transformations" form an integral part of this Recommendation and are considered normative. Because the data model is the same whether the original document was XML 1.0 or XML 1.1, the semantics of XSLT processing do not depend on the version of XML used by the original document. There is no reason in principle why all the documents used in a single transformation must conform to the same version of XML.

2.2 XSL Namespace

The XSL namespace has the URI http://www.w3.org/1999/XSL/Format.

Note:

The 1999 in the URI indicates the year in which the URI was allocated by the W3C. It does not indicate the version of XSL being used.

XSL processors must use the XML namespaces mechanism ([XML Names] or [XML Names 1.1]) to recognize elements and attributes from this namespace. Elements from the XSL namespace are recognized only in the stylesheet, not in the source document. Implementors must not extend the XSL namespace with additional elements or attributes. Instead, any extension must be in a separate namespace. The expanded-name of extension elements must have a non-null namespace URI.

This specification uses the prefix fo: for referring to elements in the XSL namespace. However, XSL stylesheets are free to use any prefix, provided that there is a namespace declaration that binds the prefix to the URI of the XSL namespace.

An element from the XSL namespace may have any attribute not from the XSL namespace, provided that the expanded-name of the attribute has a non-null namespace URI. The presence of such attributes must not change the behavior of XSL elements and functions defined in this document. This means that an extension attribute may change the processing of an FO, but only provided that the constraints specified by XSL on that FO remain satisfied. Thus, an XSL processor is always free to ignore such attributes, and must ignore such attributes without giving an error if it does not recognize the namespace URI. Such attributes can provide, for example, unique identifiers, optimization hints, or documentation.

It is an error for an element from the XSL namespace to have attributes with expanded-names that have null namespace URIs (i.e., attributes with unprefixed names) other than attributes defined in this document.

Note:

The conventions used for the names of XSL elements, attributes, and functions are as follows: names are all lowercase, hyphens are used to separate words, dots are used to separate names for the components of complex datatypes, and abbreviations are used only if they already appear in the syntax of a related language such as XML or HTML.