XML in a Nutshell, 3rd Edition

Simple Links

A simple link defines a one-way connection between two resources. The source or starting resource of the connection is the link element itself. The target or ending resource of the connection is identified by a Uniform Resource Identifier (URI). The link goes from the starting resource to the ending resource. The starting resource is always an XML element. The ending resource may be an XML document, a particular element in an XML document, a group of elements in an XML document, a span of text in an XML document, or something that isn’t a part of an XML document, such as an MPEG movie or a PDF file. The URI may be something other than a URL, perhaps a book ISBN number like urn:isbn:1565922247.

A simple XLink is encoded in an XML document as an element of arbitrary type that has an xlink:type attribute with the value simple and an xlink:href attribute whose value is the URI of the link target. The xlink prefix must be mapped to the http://www.w3.org/1999/xlink namespace URI. As usual, the prefix can change as long as the URI stays the same. For example, suppose this novel element appears in a list of children’s literature and we want to link it to the actual text of the novel available from the URL ftp://archive.org/pub/etext/etext93/wizoz10.txt:

<novel>
  <title>The Wonderful Wizard of Oz</title>
  <author>L. Frank Baum</author>
  <year>1900</year>
</novel>

We give the novel element an xlink:type attribute with the value simple, an xlink:href attribute that contains the ...