Hour22.Addressing and Linking XML Documents

Hour 22. Addressing and Linking XML Documents

Writing for the Web without linking is like eating without digesting. It's literary bulimia.

Doc Searls

So maybe that quote is a little strong in regard to the importance of linking on the Web, but the underlying point is still very much valid. Just as XML has been leveraged to improve other facets of the Web such as the core syntax and structure of HTML, so is it being used to improve upon the very linking mechanism that forms the interconnections between pages on the Web. I'm referring to XLink, which is the XML linking technology that allows you to carry out advanced linking between XML documents. Coupled with another important XML technology called XPointer, XLink builds on the premise of HTML hyperlinks but goes several steps further in supporting advanced linking features such as two-way links. Although XML linking is still a relatively new technology, it is already having an impact on how information is connected on the Web.

Linking XML documents goes hand in hand with addressing XML documents. Yet another XML-related technology called XPath makes it possible to specify exactly where XML content is located. Just as your mailing address helps you to remember where you live, XPath provides a means of remembering where nodes are located in XML documents. Okay, you probably don't rely on your mailing address to remember where you live, but you will rely on XPath if you use technologies such as XSLT, XLink, or XPointer, which must reference parts of XML documents. XPath is the enabling technology that allows you to drill down into XML documents and reference individual pieces of information.

In this hour, you'll learn

• How to navigate through an XML document using XPath patterns

• How to build powerful expressions using XPath patterns and functions

• What technologies come together to support linking in XML

• How to reference document fragments with XPointer

• How to link XML documents with XLink