blocks|key|1335077|text|鉴于XPath语法支持以下功能，这对于完整的XPath实现是否可行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1335078|/AAA/XXX/following::*|code-block|syntax|javascript|1335079|和|1335080|/AAA/BBB/following-sibling::*|1335081|这意味着前瞻性的需求？也就是说，从一个特定的节点，你无论如何都要加载文档的其余部分。|1335082|Nux库(特别是StreamingPathFilter)的文档说明了这一点，并引用了一些依赖于XPath子集的实现。Nux声称可以执行一些流查询功能，但鉴于上述情况，在XPath实现方面将存在一些限制。|offset|length|1335083|entityMap|0|LINK|mutability|MUTABLE|url|http://acs.lbl.gov/nux/|1|http://acs.lbl.gov/nux/api/nux/xom/xquery/StreamingPathFilter.html^0|0|0|0|0|0|0|3|0|8|J|1|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|15|8|@]|9|@$O|16|P|17|1|18]|$O|19|P|1A|1|1B]]|A|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]|Y|$5|T|U|V|A|$W|Z]]]]

Would this be practical for a complete XPath implementation, given that XPath syntax allows for:

<pre><code>/AAA/XXX/following::*
</code></pre>

and

<pre><code>/AAA/BBB/following-sibling::*
</code></pre>

which implies look-ahead requirements ? i.e. from a particular node you're going to have to load the rest of the document anyway.

The doc for the <a href="http://acs.lbl.gov/nux/" rel="nofollow noreferrer">Nux</a> library (specifically <a href="http://acs.lbl.gov/nux/api/nux/xom/xquery/StreamingPathFilter.html" rel="nofollow noreferrer">StreamingPathFilter</a>) makes this point, and references some implementations that rely on a subset of XPath. Nux claims to perform some streaming query capability, but given the above there will be some limitations in terms of XPath implementation.

blocks|key|939626|text|XSLT3.0提供了+，随着XSLT3.0+W3C规范成为W3C推荐标准，它将成为一种标准。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|939627|在撰写本文时(2011年5月)，Saxon提供了一些。|939628|entityMap^0|0|A|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

XSLT 3.0 provides <a href="http://www.w3.org/TR/xslt-21/#streaming" rel="nofollow">streaming mode of processing</a> and this will become a standard with the XSLT 3.0 W3C specification becoming a W3C Recommendation.

At the time of writing this answer (May, 2011) Saxon provides some <a href="http://www.saxonica.com/documentation/sourcedocs/streaming/streaming-templates.xml" rel="nofollow">support for XSLT 3.0 streaming</a> .

blocks|key|4156464|text|有几个选项：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4156465|在可能的情况下使用投影和流的|4156466|DataDirect+Technologies+sells+an+XQuery+implementation。它可以处理数It范围内的文件-例如，大于可用内存。它是一个线程安全的库，所以很容易集成。Java-only.|unordered-list-item|offset|length|4156467|Saxon是一个开源版本，有一个价格适中、价格较高的表亲，它将在某些情况下提供流媒体服务。also.|4156468|MarkLogic和eXist是XML数据库，如果将您的XML加载到其中，它们将以相当智能的方式处理XPaths。|4156469|4156470|entityMap|0|LINK|mutability|MUTABLE|url|http://www.xquery.com/architecture/|1|http://www.saxonica.com/|2|http://www.marklogic.com/|3|http://exist.sourceforge.net/^0|0|0|0|1I|0|0|0|5|1|0|0|9|2|A|5|3|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|13|8|@]|9|@$G|14|H|15|1|16]]|A|$]]|$1|I|3|J|5|F|7|17|8|@]|9|@$G|18|H|19|1|1A]]|A|$]]|$1|K|3|L|5|F|7|1B|8|@]|9|@$G|1C|H|1D|1|1E]|$G|1F|H|1G|1|1H]]|A|$]]|$1|M|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|U]]|V|$5|Q|R|S|A|$T|W]]|X|$5|Q|R|S|A|$T|Y]]|Z|$5|Q|R|S|A|$T|10]]]]

There are several options:

<ul>
<li><a href="http://www.xquery.com/architecture/" rel="nofollow noreferrer">DataDirect Technologies sells an XQuery implementation</a> that employs projection and streaming, where possible. It can handle files into the multi-gigabyte range - e.g. larger than available memory. It's a thread-safe library, so it's easy to integrate. Java-only.</li>
<li><a href="http://www.saxonica.com" rel="nofollow noreferrer">Saxon</a> is an open-source version, with a modestly-priced more expensive cousin, which will do streaming in some contexts. Java, but with a .net port also.</li>
<li><a href="http://www.marklogic.com" rel="nofollow noreferrer">MarkLogic</a> and <a href="http://exist.sourceforge.net/" rel="nofollow noreferrer">eXist</a> are XML databases that, if your XML is loaded into them, will process XPaths in a fairly intelligent fashion.</li>
</ul>

blocks|key|32365|text|试试Joost。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|32366|entityMap|0|LINK|mutability|MUTABLE|url|http://joost.sourceforge.net/^0|2|5|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Try <a href="http://joost.sourceforge.net/" rel="nofollow noreferrer">Joost</a>.

blocks|key|32422|text|虽然我没有使用它的实际经验，但我认为值得一提的是QuiXProc+(+http://code.google.com/p/quixproc/+)。它是一种XProc的流式方法，并使用为XPath等提供流式支持的库。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|32423|entityMap|0|LINK|mutability|MUTABLE|url|http://code.google.com/p/quixproc/^0|Z|Y|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Though I have no practical experience with it, I thought it is worth mentioning QuiXProc ( <a href="http://code.google.com/p/quixproc/" rel="nofollow">http://code.google.com/p/quixproc/</a> ). It is a streaming approach to XProc, and uses libraries that provide streaming support for XPath amongst others..

blocks|key|32390|text|FWIW，我使用了Nux流过滤器xpath查询非常大(>3+3GB)的文件，它工作得很完美，占用的内存也很少。我的用例略有不同(不是以验证为中心)，但我强烈建议您尝试使用Nux。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|32391|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

FWIW, I've used Nux streaming filter xpath queries against very large (>3GB) files, and it's both worked flawlessly and used very little memory. My use case is been slightly different (not validation centric), but I'd highly encourage you to give it a shot with Nux.

blocks|key|32455|text|我想我会选择自定义代码。如果只想读取.NET文档的一些路径，XML库可以让我们非常接近目标。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|32456|因为到目前为止我看到的所有解决方案都只涉及XPath子集，所以这也是一种解决方案。不过，这个子集非常小。:)|32457|这段C#代码读取xml文件，并计算给定显式路径的节点数。您还可以使用xr["attrName"]语法轻松地对属性进行操作。|offset|length|style|CODE|32458|++int+c+=+0;
++var+r+=+new+System.IO.StreamReader(asArgs[1]);
++var+se+=+new+System.Xml.XmlReaderSettings();
++var+xr+=+System.Xml.XmlReader.Create(r,+se);
++var+lstPath+=+new+System.Collections.Generic.List<String>();
++var+sbPath+=+new+System.Text.StringBuilder();
++while+(xr.Read())+{
++++//Console.WriteLine("type+"+%2B+xr.NodeType);
++++if+(xr.NodeType+==+System.Xml.XmlNodeType.Element)+{
++++++lstPath.Add(xr.Name);
++++}

++++//+It+takes+some+time.+If+1+unit+is+time+needed+for+parsing+the+file,
++++//+then+this+takes+about+1.0.
++++sbPath.Clear();
++++foreach(object+n+in+lstPath)+{
++++++sbPath.Append('/');
++++++sbPath.Append(n);
++++}
++++//+This+takes+about+0.6+time+units.
++++string+sPath+=+sbPath.ToString();

++++if+(xr.NodeType+==+System.Xml.XmlNodeType.EndElement
++++++++%7C%7C+xr.IsEmptyElement)+{
++++++if+(xr.Name+==+"someElement"+&&+lstPath[0]+==+"main")
++++++++c%2B%2B;
++++++//+And+test+simple+XPath+explicitly:
++++++//+if+(sPath+==+"/main/someElement")
++++}

++++if+(xr.NodeType+==+System.Xml.XmlNodeType.EndElement
++++++++%7C%7C+xr.IsEmptyElement)+{
++++++lstPath.RemoveAt(lstPath.Count+-+1);
++++}
++}
++xr.Close();|code-block|syntax|javascript|32459|entityMap^0|0|0|Y|E|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@$F|T|G|U|H|I]]|9|@]|A|$]]|$1|J|3|K|5|L|7|V|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

I think I'll go for custom code. .NET library gets us quite close to the target, if one just wants to read some paths of the xml document.

Since all the solutions I see so far respect only XPath subset, this is also this kind of solution. The subset is really small though. :)

This C# code reads xml file and counts nodes given an explicit path. You can also operate on attributes easily, using <code>xr["attrName"]</code> syntax.

<pre><code> int c = 0;
 var r = new System.IO.StreamReader(asArgs[1]);
 var se = new System.Xml.XmlReaderSettings();
 var xr = System.Xml.XmlReader.Create(r, se);
 var lstPath = new System.Collections.Generic.List&lt;String&gt;();
 var sbPath = new System.Text.StringBuilder();
 while (xr.Read()) {
 //Console.WriteLine("type " + xr.NodeType);
 if (xr.NodeType == System.Xml.XmlNodeType.Element) {
 lstPath.Add(xr.Name);
 }

 // It takes some time. If 1 unit is time needed for parsing the file,
 // then this takes about 1.0.
 sbPath.Clear();
 foreach(object n in lstPath) {
 sbPath.Append('/');
 sbPath.Append(n);
 }
 // This takes about 0.6 time units.
 string sPath = sbPath.ToString();

 if (xr.NodeType == System.Xml.XmlNodeType.EndElement
 || xr.IsEmptyElement) {
 if (xr.Name == "someElement" &amp;&amp; lstPath[0] == "main")
 c++;
 // And test simple XPath explicitly:
 // if (sPath == "/main/someElement")
 }

 if (xr.NodeType == System.Xml.XmlNodeType.EndElement
 || xr.IsEmptyElement) {
 lstPath.RemoveAt(lstPath.Count - 1);
 }
 }
 xr.Close();
</code></pre>

Are there any production-ready libraries for streaming XPath expressions evaluation against provided xml-document? My investigations show that most of existing solutions load entire DOM-tree into memory before evaluating xpath expression.

Streaming XPath evaluation

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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对于所提供的xml-document，是否有用于流式XPath表达式计算的现成产品库？我的调查显示，大多数现有的解决方案都是在计算xpath表达式之前将整个DOM树加载到内存中。

问流XPath评估
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