XML Schema Complete Reference, The

4.2. XPointer

XML schema documents use schemaLocation attributes to locate other schema documents and parts of schema documents. The value of a schemaLocation is always a URI, which may include an XPointer. The schemaLocation attribute type of schema, import, and include are examples of where an XPointer might locate a schema document location.

An XPointer is nominally an extension of an XPath. The XPointer Recommendation permits— even encourages—the use of the XPath id function. There are also several XPointer specific extensions to XPath.

The XPointer Recommendation specifies expressions for returning portions of an XML document. The expression may evaluate to a node, a set of nodes, a portion of a node, or a portion of an XML document that ...