XPointer Example

Let's try to learn some basic XPointer syntax by looking at an example.

XPointer Example

In this example, we will show you how to use XPointer in conjunction with XLink to point to a specific part of another document.

We will start by looking at the target XML document (the document we are going to link to).

The Target XML Document

The target XML document is called "dogbreeds.xml" and it lists a few different dog breeds:

<?xml version="1.0" encoding="ISO-8859-1"?>

<dogbreeds>

<dog breed="Rottweiler" id="Rottweiler">
  <picture url="http://dog.com/rottweiler.gif" />
  <history>
  The Rottweiler's ancestors were probably Roman
  drover dogs.....
  </history>
  <temperament>
  Confident, bold, alert and imposing, the Rottweiler
  is a popular choice for its ability to protect....
  </temperament>
</dog>

<dog breed="FCRetriever" id="FCRetriever">
  <picture url="http://dog.com/fcretriever.gif" />
  <history>
  One of the earliest uses of retrieving dogs was to
  help fishermen retrieve fish from the water....
  </history>
  <temperament>
  The flat-coated retriever is a sweet, exuberant,
  lively dog that loves to play and retrieve....
  </temperament>
</dog>

</dogbreeds>

View the "dogbreeds.xml" file in your browser

Note that the XML document above uses id attributes on each element we may want to link to!

The Linking XML Document

Instead of linking to the entire document (as with XLink), XPointer allows you to link to specific parts of the document. To link to a specific part of a page, add a number sign (#) and an XPointer expression after the URL in the xlink:href attributes.

The expression: #xpointer(id("Rottweiler")) refers to the element in the target document, with the id value of "Rottweiler".

So the xlink:href attribute would look like this: xlink:href="http://dog.com/dogbreeds.xml#xpointer(id('Rottweiler'))"

However, XPointer allows a shorthand form when linking to an element with an id. You can use the value of the id directly, like this: xlink:href="http://dog.com/dogbreeds.xml#Rottweiler"

The following XML document refers to information of the dog breed for each of my dogs :-), all through XLink and XPointer references:

<?xml version="1.0" encoding="ISO-8859-1"?>

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

<mydog xlink:type="simple"
  xlink:href="http://dog.com/dogbreeds.xml#Rottweiler">
  <description xlink:type="simple"
  xlink:href="http://myweb.com/mydogs/anton.gif">
  Anton is my favorite dog. He has won a lot of.....
  </description>
</mydog>

<mydog xlink:type="simple"
  xlink:href="http://dog.com/dogbreeds.xml#FCRetriever">
  <description xlink:type="simple"
  xlink:href="http://myweb.com/mydogs/pluto.gif">
  Pluto is the sweetest dog on earth......
  </description>
</mydog>

</mydogs>

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