XML Pointer fromW3C. (Internet Focus).

The World Wide Web Consortium (W3C) has issued the XML Pointer Language (XPointer) Recommendation--the XPointer Framework, the XPointer element Scheme, and the XPointer xmlns Scheme. The XPointer Framework provides a lightweight extensible model for identifying parts of XML documents. The XPointer scheme allows the user to point to specific elements in XML documents and data, while the XPointer xinlnso scheme brings the power of XML Namespaces to the XPointer Framework, giving a way to avoid name collisions between schemes and provide namespace binding information for use within other schemes.

Advancement of these documents to Recommendation indicates that these W3C-developed specifications are stable, contribute to Web interoperability, and have been reviewed by the W3C Membership, who favour their adoption by the industry.

Identifying Parts of XML Documents Had Shown Limitations

When XML 1.0 was first issued as a W3C Recommendation in 1998, it included a feature called "id," which gave authors a method for identifying a specific part of a XML document in conjunction with anchors and other xml elements. However, this meant that pans of a document could only be formally identified by the author of the document, not by other users who might want to reference a particular section or fragment without an id.

The W3C XML Linking Working Group, along with the W3C XML Core Working Group, began working on ways to expand the power of linking to and identifying XML fragments. Their combined results include the W3C XML Linking Recommendation, the W3C XML Base Recommendation, and now, XPointer.

XPointer Framework Expands "Pointing" and Linking Capabilities

The XPointer Framework consists of a set of basic set of syntax rules for identifying parts or fragments of XML. It provides the mechanism essential for more full and rich implementation of XML Linking. One can still use ids as pointers into XML documents and data, but the XPointer Framework also permits new XPointer schemes for identifying XML fragments. The rules for how these XPointers are created are consistent with XML syntax. The XPointer Framework also lives up to the "Extensible" in XML, as it allows users to create and reference their own schemes.

XPointer elements Scheme Makes Simple, Elegant Use of XML Document Structure

The XPointer element scheme allows pointers to be made from some of the most common components of XML documents and data--namely elements. The element scheme allows:tor both the use of ids and the use of a list of 'pointer-pans"--numerical and text expressions which guides a software processor to a precise XML fragment.

XML Namespace Scheme for XPointer Helps Avoid Name Clashes

The Namespaces in XML Recommendation helped developers and applications identify XML Languages and make them easier to combine, eliminating both conflict and ambiguity. The XPointer xmlns scheme serves the same purpose within XPointer.

As XPointer schemes are independently developed, the use of the XPointer xmlns scheme distinguishes one scheme from another in a definitive manner. Even if the same name is used in two or more XPointer schemes, namespaces enable a processor to tell the difference, and process the XPointer correctly. The XPointer xmlns scheme also makes XPointers to be self-contained, even if they involve prefixed names which require namespace declarations for their interpretation. www.w3.org.hmtl