利用dom解析一个xml文件，我想获取\Model\packagedElement 路径下“name”属性值为“dinggou”的ownedAttribute节点，可是利用selectSingleNode（）返回的总是0，这是为啥呢？
要解析的xml如下：
<?xml version="1.0" encoding="UTF-8" ?>
- <uml:Model xmi:version="2.1" xmlns:xmi="http://schema.omg.org/spec/XMI/2.1" xmlns:uml="http://www.eclipse.org/uml2/2.1.0/UML" xmi:id="_kkgsMBeLEd60N8ipLbB6nA" name="Atmosphere">
- <packagedElement xmi:type="uml:Class" xmi:id="_0Ot84JwMEeGMlsuVTnw_dg" name="Atmosphere">
<ownedAttribute xmi:id="_0Sb_QJwMEeGMlsuVTnw_dg" name="_isTarget" visibility="private" isStatic="true" type="_0TB1IJwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0TB1IZwMEeGMlsuVTnw_dg" name="dinggou" visibility="public" type="_0TehEJwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0TLmIJwMEeGMlsuVTnw_dg" name="fabu" visibility="public" type="_0UOH8JwMEeGMlsuVTnw_dg" />
</packagedElement>
<packagedElement xmi:type="uml:PrimitiveType" xmi:id="_0TB1IJwMEeGMlsuVTnw_dg" name="bool" />
- <packagedElement xmi:type="uml:Class" xmi:id="_0TehEJwMEeGMlsuVTnw_dg" name="LocationData">
<ownedAttribute xmi:id="_0ToSEJwMEeGMlsuVTnw_dg" name="longitude" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0ToSEpwMEeGMlsuVTnw_dg" name="latitude" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0TxcAJwMEeGMlsuVTnw_dg" name="height" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0TxcAZwMEeGMlsuVTnw_dg" name="position_ang" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0T7NAJwMEeGMlsuVTnw_dg" name="pitch_ang" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0T7NAZwMEeGMlsuVTnw_dg" name="roll_ang" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
</packagedElement>
<packagedElement xmi:type="uml:PrimitiveType" xmi:id="_0ToSEZwMEeGMlsuVTnw_dg" name="double" />
- <packagedElement xmi:type="uml:Class" xmi:id="_0UOH8JwMEeGMlsuVTnw_dg" name="AtmData">
<ownedAttribute xmi:id="_0UX48JwMEeGMlsuVTnw_dg" name="wind" visibility="public" type="_0Uz90JwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0UX48ZwMEeGMlsuVTnw_dg" name="temprature" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0UhC4JwMEeGMlsuVTnw_dg" name="cloud" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0UhC4ZwMEeGMlsuVTnw_dg" name="fog" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0Uqz4JwMEeGMlsuVTnw_dg" name="visibility" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
</packagedElement>
- <packagedElement xmi:type="uml:Class" xmi:id="_0Uz90JwMEeGMlsuVTnw_dg" name="wind">
<ownedAttribute xmi:id="_0U9u0JwMEeGMlsuVTnw_dg" name="wind_u" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />
<ownedAttribute xmi:id="_0VHf0JwMEeGMlsuVTnw_dg" name="wind_v" visibility="public" type="_0ToSEZwMEeGMlsuVTnw_dg" />