📄 querying&transforming xml.htm
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<h2 align="center"><b><font face="宋体" lang="ZH-CN">查询和转换XML</font></b></h2>
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<dt>
<div align="center"><span class="normal9">作者:<br>
<a href="mailto:davidsch@microsoft.com"><b>David Schach</b></a><b>,
Microsoft Corporation<br />
<a href="mailto:jlapp@webmethods.com">Joe Lapp</a>, webMethods Inc.<br />
<a href="mailto:jonathan@texcel.no">Jonathan Robie</a>, Texcel Inc.</b></span></div>
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<td width="25%" height="92"><a name="top"></a></td>
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<ol>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3"><a href="#1">简介</a></font></span></span></li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3"><a href="#2">XSL概述</a></font></span></span></li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3"><a href="#3">附加的查询功能</a></font></span></span></li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3"><a href="#4">与XML-QL的关系
</a> </font> </span> </span>
<ol>
<p align="JUSTIFY">
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3">变量和连接</font></span></span></li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3">对象标识符</font></span></span></li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3">多重XML源的数据集成</font></span></span></li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3">数据库管理</font></span></span></li>
</ol>
<p align="JUSTIFY">
</li>
<li><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3"><a href="#5">总结</a>
</font></span></span></li>
</ol>
<font face="宋体" lang="ZH-CN" size=3>
<hr size="1" align="center" width="100%">
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1. <font face="宋体" lang="ZH-CN" size="3"><a name="1"></a>简介</font>
<p></p>
<p align="JUSTIFY"><font face="宋体" lang="ZH-CN" size="3"><span class="normal11"><a href="../../../www.w3.org/TR/REC-xml" tppabs="http://www.w3.org/TR/REC-xml"><span class="normal105"><span class="normal105"><span class="normal105">XML1.0标准</span></span></span></a><span class="normal105"><span class="normal105"><span class="normal105">使得网上的数据交换有了标准的方式。这样必然要有一种机制，通过它能够查询XML、对获取的数据定型(包括数据滤除和排序)、XML语法间的转换以及这些数据通常在用户端的表现。</span></span></span></span></font></p>
<p align="JUSTIFY"><span class="normal105"><span class="normal105"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3"><span class="normal11"><span class="normal105">在“XM<span class="normal105">L查询语言XML-QL”<span class="normal105">(
<a href="../../../www.w3.org/TR/NOTE-xml-ql/index.htm" tppabs="http://www.w3.org/TR/NOTE-xml-ql/" class="normal105">http://www.w3.org/TR/NOTE-xml-ql/</a>
)</span>中建议的方法和正由<a href="../../../www.w3.org/TR/WD-xsl" tppabs="http://www.w3.org/TR/WD-xsl" class="normal105">XSL工作小组</a>定义和转换</span>语言有着惊人的相似。这两种方法的结合将会为XML提供强大而灵活的查询和转换语言</span></span><span class="normal105">。</span></font></span></span></span></p>
<p align="JUSTIFY"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3"><span class="normal11"><span class="normal105">XSL和XSL模式语言作为查询和转换语言发展的基础有独特的优势:</span></span></font></span></span></span></span></p>
<ol>
<p align="JUSTIFY">
<li><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal11"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3" class="normal105">W3C正在研究中</font></span></span></span></span></span></span></span></span></span></span></li>
<li><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal11"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">模式(查询)语法、转换功能和格式化语法的模块化</span></font></span></span></span></span></span></span></span></span></span></li>
<li><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal11"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">XML定型和表现方式的生成有统一的机制</span></font></span></span></span></span></span></span></span></span></li>
<li><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal11"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">规则、非规则甚至是递归的数据结构都能适用</span></font></span></span></span></span></span></span></span></span></span></li>
</ol>
2. <a name="2"></a>XSL概述
<p><font face="宋体" lang="ZH-CN" size=3 class="normal105">XSL由三个模块组成:</font></p>
<ol>
<p align="JUSTIFY">
<li><font face="宋体" lang="ZH-CN" size="3" class="normal105">XSL模式(XSL
Pattern):</font></li>
<p></p>
<p align="JUSTIFY"><font face="宋体" lang="ZH-CN" size="3" class="normal105">XSL定义一种“模式”句法标识XML文档中的节点。这项功能类似于SQL中WHERE语句.</font></p>
<p align="JUSTIFY">
<li><font face="Albertus (W1)" size=3><span class="normal105"><span class="normal105">“</span></span></font><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size=3 class="normal105">XSL</font><font face="Albertus (W1)" size=3><span class="normal105">”</span></font><font face="宋体" lang="ZH-CN" size=3 class="normal105">名域</font></span><font face="宋体" lang="ZH-CN" size=3 class="normal105">(</font><font face="Albertus (W1)" size=3 class="normal105">“</font><font face="宋体" lang="ZH-CN" size=3 class="normal105">XSL</font><font face="Albertus (W1)" size=3><span class="normal105">”</span></font><span class="normal105"><font face="宋体" lang="ZH-CN" size=3><span class="normal105">
</span></font></span><font face="宋体" lang="ZH-CN" size=3><span class="normal105">Namespace):</span></font></span></li>
<p></p>
<p align="JUSTIFY"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">XSL的转换部分能表达为一个XML名域，它控制将查询结果具体化为一个XML文档。</span></font></span></p>
<p align="JUSTIFY">
<li><font face="Albertus (W1)" size=3><span class="normal105"><span class="normal105">“</span></span></font><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size=3>fo</font><font face="Albertus (W1)" size=3><span class="normal105">”</span></font><span class="normal105"><font face="宋体" lang="ZH-CN" size=3><span class="normal105">名域(</span></font><font face="Albertus (W1)" size=3 class="normal105">“</font></span><font face="宋体" lang="ZH-CN" size=3 class="normal105">fo</font><font face="Albertus (W1)" size=3 class="normal105">”</font><font face="宋体" lang="ZH-CN" size=3>
<span class="normal105">Namespace):</span></font></span></span></li>
<p></p>
</ol>
<p align="JUSTIFY"><font face="宋体" lang="ZH-CN" size="3"><span class="normal11"><span class="normal105">XSL格式化的功能可以用一个XML的语法文件来表达。</span></span></font></p>
<p align="JUSTIFY"><span class="normal11"><span class="normal11"><font face="宋体" lang="ZH-CN" size=3><span class="normal11"><span class="normal105">XSL模式句法还比较简洁，不能提供强大的查询能力。它参照了目录导航的方法。作为一种基于字符串的语法，它能够在属性值、脚本语言和URL中定位。</span></span></font><span class="normal105"><span class="normal11"><font face="Albertus (W1)" size=3><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105">“</span></span></span></span></span></span></font><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size=3><span class="normal105">XSL</span></font><font face="Albertus (W1)" size=3 class="normal105">”</font></span><font face="宋体" lang="ZH-CN" size=3><span class="normal105">名域定义了一套命令集合，实现将查询结果具体</span></font></span><font face="宋体" lang="ZH-CN" size=3 class="normal105">化为XML</font></span><font face="宋体" lang="ZH-CN" size=3><span class="normal105">。一个XSL文档包括XSL名域中规定的元素，他们可能是</span></font></span></span></span></span></span></span><span class="normal105"><span class="normal105"><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size=3 class="normal105">:</font></span></span></span></span></span></p>
<ol>
<p align="JUSTIFY">
<li><span class="normal11"><font face="宋体" lang="ZH-CN" size="3" class="normal105">定义构造部分输出的模块</font></span></li>
<li><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">对来自</span><span class="normal105">XML源文件中的数据应用模板</span></font></li>
<li><font face="宋体" lang="ZH-CN" size="3" class="normal105">将该模板结合查询</font></li>
<li><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">将一套这样的查询</span>-<span class="normal105">模板结合进行组合</span>，<span class="normal105">用于内部或者递归处理</span></font></li>
<li><font face="宋体" lang="ZH-CN" size="3" class="normal105">将查询结果进行过滤和排序</font></li>
<p></p>
</ol>
<p align="JUSTIFY"><font face="宋体" lang="ZH-CN" size=3><span class="normal105">XSL的格式化性能用XML的</span></font>“<span class="normal105"><font face="宋体" lang="ZH-CN" size=3 class="normal105">fo</font></span><font face="Albertus (W1)" size=3 class="normal105">”</font><font face="宋体" lang="ZH-CN" size=3><span class="normal105">名域来表示，它完全独立于整个转换过程。</span></font></p>
<p align="JUSTIFY"></p>
3. <a name="3"></a><font face="宋体" lang="ZH-CN" size=3>附加的查询功能 </font>
<ol>
<p></p>
</ol>
<p><font face="宋体" lang="ZH-CN" size=3><span class="normal11"><span class="normal105">由Microsoft、Texcel和Webmethods合写的相关文档</span></span></font><span class="normal11"><font face="Albertus (W1)" size=3 class="normal105">”</font><font face="宋体" lang="ZH-CN" size=3><span class="normal105">XQL建议</span></font><font face="Albertus (W1)" size=3><span class="normal105"><span class="normal105"><span class="normal105">”</span></span></span></font><span class="normal105"><span class="normal105"><span class="normal105"><font face="宋体" lang="ZH-CN" size=3 class="normal105">(</font><font face="Albertus (W1)" size=3 class="normal105">“</font></span></span></span><font face="宋体" lang="ZH-CN" size=3><span class="normal105">XQL</span>
<span class="normal105">Proposal</span></font><font face="Albertus (W1)" size=3 class="normal105">”</font><font face="宋体" lang="ZH-CN" size=3><span class="normal105">)可看作为XSL模式语<span class="normal105">法</span>的扩展集，它提供了布尔操作，多种比较操作和位置、范围等性质</span>。</font></span></p>
<ol>
<div align="left"></div>
</ol>
<p><span class="normal11"><font face="宋体" lang="ZH-CN" size=3 class="normal11"><span class="normal105">类似于XSL模式语法或XQL的语言还能在XSL之外的其它许多环境中使用，用来查询个别文档或多个文档集合，无论这些文档是表达为文本或DOM节点的形式。查询语句可以作为字符串嵌入编程语言或XML</span>/<span class="normal105">HTML<span class="normal105">的属性</span>中</span>。<span class="normal105">而且</span>，<span class="normal105">这种方法并不对结果的表现格式有任何的强制</span>；<span class="normal105">结果可以返回为XML文本、指向节点的指针、表<span class="normal105">示</span>文档区域的结构或者为如字符串、整数、布尔数、数组等原始结构。其灵活性允许这些语言能在W3C<span class="normal105">的</span>许多环境中使用。</span></font></span></p>
<p>4. <a name="4"></a><font face="宋体" lang="ZH-CN" size=3>与XML-QL的关系 </font></p>
<ol>
<p></p>
</ol>
<p align="JUSTIFY"><font face="宋体" lang="ZH-CN" size="3"><span class="normal11"><span class="normal105">XML-QL阐述的许多功能常与XSL转换和模式语言提供的功能类似。两种方式都是块结构且面向模板，<span class="normal105">都能返<span class="normal105">回</span>树</span>或图表</span>。<span class="normal105">在输出中生成新元素以及对XML进行查询。最大的差别在于各自的语法。XSL采用类似URL的语法来规定模式、查询和XML的内在结构对查询块定界。</span></span></font></p>
<p align="JUSTIFY"></p>
<p align="JUSTIFY"><span class="normal11"><span class="normal11"><font face="宋体" lang="ZH-CN" size="3"><span class="normal105">这种方式的基本结构是:</span></font></span></span></p>
<p align="JUSTIFY"><span class="normal105"><font face="宋体" lang="ZH-CN" size="3" class="normal105"><xsl:for-each
select = "XSL pattern"><br>
<!-- Construct result --><br>
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