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Re: 1) Position of keyed element, 2) Determining uniqu

Subject: Re: 1) Position of keyed element, 2) Determining unique attribute values
From: Timothy Lebo <timothy.lebo@xxxxxxxxxxx>
Date: Thu, 12 Jan 2006 07:14:00 -0500
timothy lebo
Considering the cost, I would rather the pre-pass that I was trying to avoid.

Is it possible to place an <xsl:attribute> as a child of a <xsl:copy- of select="."> to augment the element with my new ID? Or do I need to enumerate xsl:element/xsl:attribute for all elements and attributes possible in my input?

Thanks,
Tim

On Jan 12, 2006, at 6:49 AM, Michael Kay wrote:

position() doesn't give you the position of a node in the input tree, it
gives you its position within whatever sequence of nodes that you are
processing at the time. For the position in the input tree, use xsl:number,
or something like count(preceding::object). This is potentially quite
expensive, if performance is an issue you might be better off to do a
pre-pass copying the tree and allocating numbers as you go, storing the
numbers in a new attribute.


In XSLT 2.0 you can easily get the distinct attribute names using
distinct-values(//attribute/@name).

Michael Kay
http://www.saxonica.com/

-----Original Message-----
From: Timothy Lebo [mailto:timothy.lebo@xxxxxxxxxxx]
Sent: 12 January 2006 11:41
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject:  1) Position of keyed element, 2) Determining
unique attribute values

Greetings,

In short, I am attempting to transfom something that looks like:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<object id="a">
    <attribute name="color" value="red"/>
</object>
<object id="b">
     <attribute name="size" value="big"/>
</object>
<object id="c">
     <attribute name="size" value="small"/>
     <attribute name="color" value="purple"/>
</object>
<link fromobject="c" toobject="b"/>
</root>

into:
<?xml version="1.0" encoding="UTF-8"?>
<output>
   <thing id="1"/>
   <thing id="2"/>
   <thing id="3"/>
   <attributes name="color">
      <attribute idref="1" value="red"/>
      <attribute idref="3" value="purple"/>
   </attributes>
   <attributes name="size">
      <attribute idref="2" value="big"/>
      <attribute idref="3" value="small"/>
</attributes>
<relation fromthing="3" tothing="2"/>
</output>

My solution, listed below, has two problems:

1) Obtaining the positional information of elements in the input tree
from different context nodes.

2) Unable to determine all unique values of //attribute/@name to group
into the attributes element. (These would then be processed with the
solution to #1)


The the 'thing' IDs in the output MUST be non-negative integers, so
generate-id is out. I thought that it would be nice (and aesthetic,
IMHO) to use the position of the 'object's to assign IDs for the
'thing's. However, when I try to obtain positional information from
the input tree with position(), I get the location of the node in the
result node set of the xpath that selects the nodes, which is always
"1".

Any solutions with XSLT 2.0 constructs would be much appreciated. I
haven't followed the developments within the last three years and am
having some difficulty appreciating its full benefits.

Highest regards,
Tim Lebo

XSLT Processor: saxonb8.6.1


My current attempt is:


<?xml version="1.0"?>
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="2.0">
<xsl:output method="xml" indent="yes"/>

<xsl:key name="objects" match="object" use="@id"/>

<xsl:template match="/">
<xsl:element name="output">
    <xsl:apply-templates select="//object"/>
    <xsl:apply-templates select="//object" mode="attributes"/>
    <xsl:apply-templates select="//link"/>
</xsl:element>
</xsl:template>

<xsl:template match="object">
<xsl:element name="thing">
    <xsl:attribute name="id" select="position()"/>
</xsl:element>
</xsl:template>

<xsl:template match="object" mode="attributes">
<xsl:element name="attributes">
    <xsl:attribute name="name" select="'WRONG: attribute elements
should be grouped by attribute/@name, not by object/@id'"/>
    <xsl:apply-templates select="attribute">
      <xsl:with-param name="id" select="position()"/>
    </xsl:apply-templates>
</xsl:element>
</xsl:template>

<xsl:template match="attribute">
<xsl:param name="id"/>
<xsl:element name="attribute">
    <xsl:attribute name="idref" select="$id"/>
    <xsl:attribute name="{@name}" select="@value"/>
</xsl:element>
</xsl:template>

<xsl:template match="link">
<xsl:variable name="toobjectID" select="@toobject"/>
<xsl:element name="relation">
<xsl:attribute name="fromthing"
select="key('objects',@fromobj
ect)/position()"/>
<xsl:attribute name="tothing"
select="//object[@id=$toobjectID]/position()"/>
<xsl:attribute name="NB" select="'WRONG: ids should be position of
input object elmenents (3,2)'"/>
</xsl:element>
</xsl:template>


</xsl:transform>

and the output is:
<?xml version="1.0" encoding="UTF-8"?>
<output>
   <thing id="1"/>
   <thing id="2"/>
   <thing id="3"/>
   <attributes name="WRONG: attribute elements should be grouped by
attribute/@name , not by object/@id">
      <attribute idref="1" color="red"/>
   </attributes>
   <attributes name="WRONG: attribute elements should be grouped by
attribute/@name , not by object/@id">
      <attribute idref="2" size="big"/>
   </attributes>
   <attributes name="WRONG: attribute elements should be grouped by
attribute/@name , not by object/@id">
      <attribute idref="3" size="small"/>
      <attribute idref="3" color="purple"/>
   </attributes>
   <relation fromthing="1" tothing="1"
             NB="WRONG: ids should be position of input object
elmenents (3,2)"/>
</output>

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