<cknell(_at_)onebox(_dot_)com> wrote in message
news:B0018919762(_at_)vljcms13(_dot_)ucmretail(_dot_)internal(_dot_)callsciences(_dot_)com(_dot_)(_dot_)(_dot_)
==========> Direction of graph
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/ |__B__|
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|__A__| |__D__|
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\ ______/
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|__C__|
I'm working on producing a network diagram in SVG by processing an XML
document with XSLT. Above is a symbolic representation of the output. The
relationship between nodes in the graph can't be represented directly in XML
because it isn't a tree (Node D has two parents which isn't allowed in XML).
Here is a simplified sample of the XML document:
<network>
<node>
<node-id>A</node-id>
<predecessor-id></predecessor-id>
<successor-id>B</successor-id>
</node>
<node>
<node-id>B</node-id>
<predecessor-id>A</predecessor-id>
<successor-id>D</successor-id>
</node>
<node>
<node-id>C</node-id>
<predecessor-id>A</predecessor-id>
<successor-id>D</successor-id>
</node>
<node>
<node-id>D</node-id>
<predecessor-id>B</predecessor-id>
<predecessor-id>C</predecessor-id>
<successor-id></successor-id>
</node>
</network>
In my stylesheet I have a template that matches <node>. For the purpose of
positioning the SVG elements I want to determine how many other nodes have a
<predecessor-id> that matches one of the <predecessor-id> children of the
context <node>. In addition to determining how many "siblings" a <node> has,
I also want to know where the context node is in document order relation to
these "siblings".
The <node> elements with common <predecessor-id> values would be, in the
context of the network diagram, "siblings". Of course in the XML document
all the <node> elements are siblings in the XPath sense.
To determine the number of siblings a <node> element has, I thought I
would count the elements in the intersection of the set of <predecessor-id>
children of the context node with the set of <predecessor-id> children of
all the other <node> elements. I modelled the expression on the example
shown on page 425 of the XSLT Programmer's Reference 2nd Edition.
Here is a simplfied stylesheet:
<?xml version="1.0" encoding="UTF-8" ?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<xsl:output method="xml" indent="yes" encoding="UTF-8" />
<xsl:template match="/">
<xsl:apply-templates />
</xsl:template>
<xsl:template match="network">
<xsl:apply-templates />
</xsl:template>
<xsl:template match="node">
<xsl:variable name="this-node-id" select="node-id" />
<xsl:variable name="this-predecessor-nodes" select="predecessor-id" />
<xsl:variable name="other-predecessor-nodes"
select="/network/node[node-id != $this-node-id]" />
<xsl:variable name="sibling-cnt"
select="count($this-predecessor-nodes[count(. | $other-predecessor-nodes) !=
count($other-predecessor-nodes)])" />
This node id = <xsl:value-of select="$this-node-id" />
Sibling count = <xsl:value-of select="$sibling-cnt" />
</xsl:template>
</xsl:stylesheet>
This yielded the following output:
<?xml version="1.0" encoding="UTF-8"?>
This node id = A
Sibling count = 1
This node id = B
Sibling count = 1
This node id = C
Sibling count = 1
This node id = D
Sibling count = 2
It the intersection operation didn't do what I expected. I expected that
nodes A and D would have a Sibling count of 0 and that nodes B and C would
each have a sibling count of 1.
Could anyone tell me where I'm going wrong and point me in the right
direction?
Thanks.
The reason is you're mixing node-identity with value-identity. The XPath
expression for intersection of two node-sets selects the *identical* nodes
from the two node-sets. In your case you want to find all nodes with the
same *value*.
Here's a transformation, which produces what you want:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<xsl:output method="xml" indent="yes" encoding="UTF-8" />
<xsl:template match="/">
<xsl:apply-templates />
</xsl:template>
<xsl:template match="network">
<xsl:apply-templates />
</xsl:template>
<xsl:template match="node">
<xsl:variable name="this-node-id" select="node-id" />
<xsl:variable name="this-predecessor-nodes"
select="/*/node[node-id = current()/node-id]/predecessor-id" />
<xsl:variable name="other-predecessor-nodes"
select="/*/node[node-id != $this-node-id]/predecessor-id" />
<xsl:variable name="sibling-cnt"
select="count($other-predecessor-nodes
[. =$this-predecessor-nodes]
)" />
This node id = <xsl:value-of select="$this-node-id" />
Sibling count = <xsl:value-of select="$sibling-cnt" />
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on your source.xml:
<network>
<node>
<node-id>A</node-id>
<predecessor-id></predecessor-id>
<successor-id>B</successor-id>
</node>
<node>
<node-id>B</node-id>
<predecessor-id>A</predecessor-id>
<successor-id>D</successor-id>
</node>
<node>
<node-id>C</node-id>
<predecessor-id>A</predecessor-id>
<successor-id>D</successor-id>
</node>
<node>
<node-id>D</node-id>
<predecessor-id>B</predecessor-id>
<predecessor-id>C</predecessor-id>
<successor-id></successor-id>
</node>
</network>
the wanted result is produced:
This node id = A
Sibling count = 0
This node id = B
Sibling count = 1
This node id = C
Sibling count = 1
This node id = D
Sibling count = 0
One final remark: the chosen representation of the graph is not good at all.
I'd recommend a better one, e.g. the standard for graph representation --
graphML.
Hope this helped.
Cheers,
Dimitre Novatchev ,
FXSL developer,
http://fxsl.sourceforge.net/ -- the home of FXSL
Resume: http://fxsl.sf.net/DNovatchev/Resume/Res.html
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list