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Re: reproducing the hierarchical structure of a subset
Subject: Re: reproducing the hierarchical structure of a subset of nodes from a document
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Fri, 10 Jun 2011 15:50:39 +0100
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Well, I'll forget that you said XSLT 1.0. Wash your mouth out.
In XSLT 2.0, it's a recursive grouping problem (with the depth of
recursion equal to the maximum depth of the original document.)
First group the paths by their first token: the grouping keys define the
elements at the first level of hierarchy. Within the for-each-group,
strip off the first token, and recurse until the group is empty.
Something like this:
<xsl:function name="f:group">
<xsl:param name="paths">
<xsl:for-each-group select="$paths" group-by="tokenize(.)[1]">
<xsl:element name="{current-grouping-key()}">
<xsl:sequence select="f:group(for $p in current-group() return
remove(tokenize($p), 1)"/>
</xsl:element>
</xsl:for-each-group>
</xsl:function>
Michael Kay
Saxonica
On 10/06/2011 15:26, trubliphone wrote:
Hello,
I have an algorithmic problem I haven't been able to solve. I was
hoping somebody on this list could offer me some advice.
I do have a solution in pure XQuery, but that requires recursion
through a potentially massive XML document which is too inefficient
for production use. So, I am trying to come up with another way and I
wondered if XSL might do the trick.
Suppose I have some arbitrary XML file:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<foo>
<bar>one</bar>
<foo>
<bar>two</bar>
</foo>
<foo>
<bar>three</bar>
</foo>
</foo>
<foo>
<bar>four</bar>
<foo>
<foo>
<bar>five</bar>
</foo>
</foo>
</foo>
</root>
Now, suppose there is a user-provided XPath expression to find
particular nodes in that file:
$query := "//foo/bar"
I understand that I cannot, in pure XSLT v1.0, easily evaluate that
string against the document and return the desired nodes. That's
okay, I can do it in other languages.
After evaluating that string, I wind up with the following node sequence:
(<bar>one</bar>,<bar>two</bar>,<bar>three</bar>,<bar>four</bar>,
<bar>five</bar>)
But I need to recreate the original hierarchical structure of those
nodes. So what I really want is this:
<bar>one
<bar>two</bar>
<bar>three</bar>
</bar>
<bar>four
<bar>five</bar>
</bar>
To help, I can get the "context path" of each node as follows:
one: /root[1]/foo[1]/bar[1]
two: /root[1]/foo[1]/foo[1]/bar[1]
three: /root[1]/foo[1]/foo[2]/bar[1]
four: /root[1]/foo[2]/bar[1]
five: /root[1]/foo[2]/foo[1]/foo[1]/bar[1]
So I have the following sequence to work with that I can run an XSL template on:
(
<node cp="/root[1]/foo[1]/bar[1]"><bar>one</bar></node>,
<node cp="/root[1]/foo[1]/foo[1]/bar[1]"><bar>two</bar></node>,
<node cp="/root[1]/foo[1]/foo[2]/bar[1]"><bar>three</bar></node>,
<node cp="/root[1]/foo[2]/bar[1]"><bar>four</bar></node>,
<node cp="/root[1]/foo[2]/foo[1]/foo[1]/bar[1]"><bar>five</bar></node>
)
My question is how to turn that into a tree that recreates the
original hierarchical structure?
Many thanks for your help.
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