Oops,
At 05:19 AM 2/19/2004, Dimitre wrote:
In this and similar problems one can re-use the identity transformation,
which processes strictly one node at a time (would a native English
speaker, please, suggest a good name? The best I could arrive at was "one
node at a time identity transformation"):
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes"/>
<xsl:template match="@* | node()">
<xsl:copy>
<xsl:apply-templates select="@*"/>
<xsl:apply-templates select="node()[1]"/>
</xsl:copy>
<xsl:apply-templates select="following-sibling::node()[1]"/>
</xsl:template>
</xsl:stylesheet>
In my last e-mail I was reading too quickly, and neglected to observe,
before answering, that you're stepping forward one node at a time along the
following-sibling axis.
I'd probably distinguish this from the usual identity
transform-by-tree-traversal by referring to its "stepping forward".
"Stepping forward" or even "tiptoeing forward" (since you're often
conducting a test as you go) is the way I usually describe the family of
methods that traverse the following-sibling axis to allow this kind of
fine-grained control.
In practice, however, I also find that XSLT newbies need the concepts
explained in any case, and more experienced users get the idea quickly from
a short description ("no, I mean an identity transform that steps forward
one node at a time along the following-sibling axis"), so that the lack of
a fixed technical terminology for all this stuff doesn't really hurt that much.
"Muenchian grouping" is probably the exception that proves this rule, since
that method is tricky enough to defy a one-line description, but the
problem it deals with is common enough to come up often....
Cheers,
Wendell
This transformation produces the same results as the more well-known
identity rule.
The difference is that we now have the finest possible grain-level of
controll as every xsl:apply-templates instruction above always selects at
most one node.
It is trivial to add parameters and to override the one-at-a-time identity
for elements. Thus we finally have:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes"/>
<xsl:template match="@* | node()">
<xsl:param name="pnAncestors" select="0"/>
<xsl:param name="pnPreceding" select="0"/>
<xsl:copy>
<xsl:apply-templates select="@*"/>
<xsl:apply-templates select="node()[1]">
<xsl:with-param name="pnAncestors"
select="$pnAncestors+1"/>
<xsl:with-param name="pnPreceding"
select="$pnPreceding"/>
</xsl:apply-templates>
</xsl:copy>
<xsl:apply-templates select="following-sibling::node()[1]">
<xsl:with-param name="pnAncestors"
select="$pnAncestors"/>
<xsl:with-param name="pnPreceding"
select="$pnPreceding+1"/>
</xsl:apply-templates>
</xsl:template>
<xsl:template match="*">
<xsl:param name="pnAncestors" select="0"/>
<xsl:param name="pnPreceding" select="0"/>
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:attribute name="_id">
<xsl:value-of select=
"concat(name(), '_',
$pnAncestors, '_',
$pnPreceding
)"/>
</xsl:attribute>
</xsl:copy>
<xsl:apply-templates select="node()[1]">
<xsl:with-param name="pnAncestors"
select="$pnAncestors+1"/>
<xsl:with-param name="pnPreceding"
select="$pnPreceding"/>
</xsl:apply-templates>
<xsl:apply-templates select="following-sibling::node()[1]">
<xsl:with-param name="pnAncestors"
select="$pnAncestors"/>
<xsl:with-param name="pnPreceding"
select="$pnPreceding+1"/>
</xsl:apply-templates>
</xsl:template>
</xsl:stylesheet>
This transformation is not long, it can be written almost mechanically, it
makes exactly one pass over the tree and it has a linear time complexity
(checked with inputs of different size).
Cheers,
Dimitre Novatchev
FXSL developer,
http://fxsl.sourceforge.net/ -- the home of FXSL
Resume: http://fxsl.sf.net/DNovatchev/Resume/Res.html
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