XPointer allows you to walk the tree of nodes that an XML document is comprised of to address a specific node or nodes. XPointer expands the syntax set forth by XPath to provide a means of creating fragment identifiers, which are used to specify parts of documents. XPointer provides considerably more control over the referencing of XML document data than the hyperlink approach employed by HTML. For example, XPointer allows you to do things such as address an element with a given value within a list of elements of a given type. You use XPointer
Uche Ogbuji wrote a good article on XML.com here is a summary: "I’m still getting my Weblogger profile here updated, but this year I transitioned from one company I co-founded to another. Zepheira provides data architecture solutions, with a focus on semantic technology. I was early on the Semantic Web bandwagon, and I almost fell off at one point because I felt the useful, modest ideas at the core had been overrun by an academic brand of technological megalomania. This year I felt the timing was right to not only renew my interest in the technology,
Introduction
This specification defines the XML Linking Language (XLink), which allows elements to be inserted into XML documents in order to create and describe Link between resources.
XLink provides a framework for creating both basic unidirectional links and more complex linking structures. It allows XML documents to:
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Assert linking relationships among more than two resources
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Associate metadata with a link
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Express links that reside in a location separate from the linked resources
An important application of XLink is in
XML Linking Language (XLink) is a generic framework for expressing links in XML documents, to complete its placement in hypertext systems such as the Web. It can be used to create simple links, such as those that are an essential part of HTML documents, or more complex types of links, such as multiended links and link databases.
XML Linking Language (XLink) Version 1.0 [W3C Recommendation] provides a generic framework for expressing links in XML documents. Hypertext, which requires linking, is the foundation of the Web, and adding sophisticated
XLink is concerned with linking itself, as the term is understood in the hypertext community: establishing (non-sequential) connections between data objects. This is distinct from addressing mechanisms such as URIs and XPointers: A URI is not properly speaking a link, just as an HREF attribute is not an A element. The XLink specification is intended to enable:
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Identifying linking elements beyond A and IMG;
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Attaching links to documents without modifying them (annotations, "stand-off" tagging, etc.);
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Providing external, symmetrical,
Summary:
The purpose of an XML namespace is to allow the deployment of XML vocabularies (in which element and attribute names are defined) in a global environment and to reduce the risk of name collisions in a given document when vocabularies are combined. For example, the MathML and SVG specifications both define the set element. Although XML data from different formats such as MathML and SVG can be combined in a single document, in this case there could be ambiguity about which set element was intended. XML namespaces reduce the risk of name
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