From http://www.w3schools.com (Copyright Refsnes Data)

XLink and XPointer Syntax

XLink Syntax

In HTML, we know (and all the browsers know!) that the <a> element defines a hyperlink. However, this is not how it works with XML. In XML documents, you can use whatever element names you want - therefore it is impossible for browsers to predict what hyperlink elements will be called in XML documents.

The solution for creating links in XML documents was to put a marker on elements that should act as hyperlinks.

Below is a simple example of how to use XLink to create links in an XML document:

<?xml version="1.0"?>

<homepages xmlns:xlink="http://www.w3.org/1999/xlink">

  <homepage xlink:type="simple"
  xlink:href="http://www.w3schools.com">Visit W3Schools</homepage>

  <homepage xlink:type="simple"
  xlink:href="http://www.w3.org">Visit W3C</homepage>

</homepages>

To get access to the XLink attributes and features we must declare the XLink namespace at the top of the document.

The XLink namespace is: "http://www.w3.org/1999/xlink".

The xlink:type and the xlink:href attributes in the <homepage> elements define that the type and href attributes come from the xlink namespace.

The xlink:type="simple" creates a simple, two-ended link (means "click from here to go there"). We will look at multi-ended (multidirectional) links later.

XPointer Syntax

In HTML, we can create a hyperlink that either points to an HTML page or to a bookmark inside an HTML page (using #).

Sometimes it is more useful to point to more specific content. For example, let's say that we want to link to the third item in a particular list, or to the second sentence of the fifth paragraph. This is easy with XPointer.

If the hyperlink points to an XML document, we can add an XPointer part after the URL in the xlink:href attribute, to navigate (with an XPath expression) to a specific place in the document.

For example, in the example below we use XPointer to point to the fifth item in a list with a unique id of "rock":

href="http://www.example.com/cdlist.xml#id('rock').child(5,item)"