XPointer 實例
讓我們通過研究一個實例來學習一些基礎的 XPointer 語法。
XPointer 實例
在本例中，我們會為您展示如何使用 XPointer 並結合 XLink 來指向另外一個文檔的某個具體的部分。
我們將通過研究目標 XML 文檔開始（即我們要鏈接的那個文檔）。
目標XML文檔
目標XML文檔名為 "dogbreeds.xml"，它列出了一些不同的狗種類：
<?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>
<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>
在您的流覽器查看 "dogbreeds.xml" 檔。
注意上面的 XML 文檔在每個我們需要鏈接的元素上使用了 id 屬性！
XML 鏈接文檔
不止能夠鏈接到整個文檔（當使用 XLink 時），XPointer 允許您鏈接到文檔的特定部分。如需鏈接到頁面的某個具體的部分，請在 xlink:href 屬性中的 URL 後添加一個井號 (#) 以及一個 XPointer 運算式。
運算式：#xpointer(id("Rottweiler")) 可引用目標文檔中 id 值為 "Rottweiler" 的元素。
因此，xlink:href 屬性會類似這樣：xlink:href="http://dog.com/dogbreeds.xml#xpointer(id('Rottweiler'))"
不過，當使用 id 鏈接到某個元素時，XPointer 允許簡寫形式。您可以直接使用 id 的值，就像這樣：xlink:href="http://dog.com/dogbreeds.xml#Rottweiler"。
下麵的 XML 文檔可引用每條狗的品種資訊，均通過 XLink 和 XPointer 來引用：
<?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>
<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>