This is the mail archive of the
xsl-list@mulberrytech.com
mailing list .
Re: XSLT 2.0 Idea: third argument for key()
- To: xsl-list at mulberrytech dot com
- Subject: Re: XSLT 2.0 Idea: third argument for key()
- From: "G. Ken Holman" <gkholman at CraneSoftwrights dot com>
- Date: Mon, 04 Sep 2000 18:26:25 -0400
- Reply-To: xsl-list at mulberrytech dot com
At 00/09/04 19:56 +0100, Jeni Tennison wrote:
>In brief: I'd like to suggest having a third argument for key(), a node
>set, such that the key only retrieves nodes with the relevant key value
>that are within this node set.
When the node set is subset based entirely on hierarchy, I do this today
using generate-id() based on the premise that generate-id() produces a name
token (that never includes a space).
>Here's an example of the second area in which this would be useful,
>restricting nodes to a known node set: say I had a document with a massive
>dataset like:
>
><athletes>
> <country id="GRB">
> <athlete event="100 metres">...</athlete>
> <athlete event="200 metres">...</athlete>
> <!-- another 400 athletes -->
> </country>
> <country id="ROI">
> <athlete event="100 metres">...</athlete>
> <athlete event="800 metres">...</athlete>
> <!-- another 400 athletes -->
> </country>
> ...
></athletes>
>
>I want to put the details of the athletes in a table, with columns being
>countries and rows being events, so I use a key to index on the event, and
>access the data for the table using:
>
> key('athletes', @event)[generate-id(parent::country) =
> generate-id(current()/parent::country)]
>
>or something similar. It would be a lot cleaner to do:
>
> key('athletes', @event, parent::country/child::athlete)
What I would do in this case is:
...
<!ENTITY lookup-athletes
"concat( generate-id(parent::country), ' ', @event )>
...
<xsl:key name="athletes" match="athlete"
use="&lookup-athletes;"/>
...
key('athletes', &lookup-athletes;)
...
>Any thoughts? Objections? Implementation issues?
Below are fragments from the solution to one of the exercises in my two-day
hands-on course where students are required to group hockey team statistics
based on the number of games played within either their division or their
conference (two separate tables).
The Muenchian Method of grouping uses *all* members of the source node tree
which isn't *directly* applicable since the grouping has to be subset by
the hierarchy. What I do is calculate the key table value to include the
generated id of the ancestral point in the source node tree. The space
delimiter ensures no possible ambiguity in the concatenated value (provided
all values are calculated the same way ... which I do using a general
entity to ensure I don't screw up my typing).
...
<!DOCTYPE xsl:stylesheet [
<!--use entities to keep typing down and promote
consistency-->
<!ENTITY lookup-games-division
"concat( generate-id(ancestor::division), ' ', g)">
<!ENTITY lookup-games-conference
"concat( generate-id(ancestor::conference), ' ', g)">
]>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:key name="games-division" match="team"
use="&lookup-games-division;"/> <!--games played within
division-->
<xsl:key name="games-conference" match="team"
use="&lookup-games-conference;"/><!--games played within
conference-->
...
<xsl:for-each select="division">
<h3><xsl:value-of select="name"/> Division</h3>
<xsl:for-each select=".//team
[generate-id(.)=generate-id(key('games-division',
&lookup-games-division;)[1])]">
...
<xsl:for-each
select="key('games-division',&lookup-games-division;)">
...
<h2><xsl:value-of select="name"/> Conference</h2>
<xsl:for-each select=".//team
[generate-id(.)=generate-id(key('games-conference',
&lookup-games-conference;)[1]
&lookup-games-conference;)[1])]">
...
<xsl:for-each
select="key('games-conference',&lookup-games-conference;)">
...
The above works quite smoothly and is the basis of how I teach students to
group subsets of the source node tree (after teaching the Muenchian Method
of grouping all found members in the source node tree).
I hope this helps.
.................... Ken
--
G. Ken Holman mailto:gkholman@CraneSoftwrights.com
Crane Softwrights Ltd. http://www.CraneSoftwrights.com/s/
Box 266, Kars, Ontario CANADA K0A-2E0 +1(613)489-0999 (Fax:-0995)
Web site: XSL/XML/DSSSL/SGML services, training, libraries, products.
Book: Practical Transformation Using XSLT and XPath ISBN1-894049-05-5
Article: What is XSLT? http://www.xml.com/pub/2000/08/holman
Next public instructor-led training: 2000-09-19/20,2000-10-03/05,
- 2000-10-09/10,2000-10-19,2000-11-06/07,2000-11-12,
- 2000-12-03/04,2001-01-27
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list