图形描述语言GraphML（2）:扩展属性

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可以为图形元素定义简单的属性来扩展Graph。属性只能使用xml中的简单类型，如string, numerical等。首先看一个例子：

<?xmlversion="1.0"encoding="UTF-8"?>
<graphmlxmlns="http://graphml.graphdrawing.org/xmlns"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
<keyid="d0"for="node"attr.name="color"attr.type="string">
<default>yellow</default>
</key>
<keyid="d1"for="edge"attr.name="weight"attr.type="double"/>
<graphid="G"edgedefault="undirected">
<nodeid="n0">
<datakey="d0">green</data>
</node>
<nodeid="n1"/>
<nodeid="n2">
<datakey="d0">blue</data>
</node>
<nodeid="n3">
<datakey="d0">red</data>
</node>
<nodeid="n4"/>
<nodeid="n5">
<datakey="d0">turquoise</data>
</node>
<edgeid="e0"source="n0"target="n2">
<datakey="d1">1.0</data>
</edge>
<edgeid="e1"source="n0"target="n1">
<datakey="d1">1.0</data>
</edge>
<edgeid="e2"source="n1"target="n3">
<datakey="d1">2.0</data>
</edge>
<edgeid="e3"source="n3"target="n2"/>
<edgeid="e4"source="n2"target="n4"/>
<edgeid="e5"source="n3"target="n5"/>
<edgeid="e6"source="n5"target="n4">
<datakey="d1">1.1</data>
</edge>
</graph>
</graphml>

上面的代码可以表示如下的图形：



<meta content="text/html; charset=utf-8" http-equiv="CONTENT-TYPE"> <meta content="StarSuite 8 (Linux)" name="GENERATOR"> <meta content="*" name="AUTHOR"> <meta content="20071029;11490000" name="CREATED"> <meta content="Seaman Wang" name="CHANGEDBY"> <meta content="20080123;13032000" name="CHANGED"> <style type="text/css"> <!-- @page { size: 21cm 29.7cm; margin: 2cm } PRE.western { font-family: "Cumberland", "Courier New", monospace } PRE.cjk { font-family: "方正宋体", monospace } PRE.ctl { font-family: "方正宋体", monospace } P { margin-bottom: 0.21cm } H3 { margin-bottom: 0.21cm } H3.western { font-family: "Albany", "Arial", sans-serif } H3.cjk { font-family: "方正黑体"; font-style: normal } H3.ctl { font-family: "Lucidasans" } --> </style>

可以看出，要增加扩展属性，需要在GraphML中增加属性定义和属性值。

属性定义部分声明了属性的标识(id)，适用范围，名称，类型和默认值(可选)。如：

<keyid="d1"for="edge"attr.name="weight"attr.type="double"/>
<keyid="d0"for="node"attr.name="color"attr.type="string">
<default>yellow</default>
</key>

属性值直接作为图形元素(node 或 edge)的子节点，如：

<nodeid="n0">
<datakey="d0">green</data>
</node>

这样，GraphML的概念包括了：