Re: [xsl] document() merge DISTINCT

["Alex Schuetz" <asc at ala dot de>]

Hi Jeni,

I have installed MSXML4 and it works !

Thanks again,
-alex

----- Original Message ----- 
From: "Jeni Tennison" <jeni@jenitennison.com>
To: "Alex Schuetz" <asc@ala.de>
Cc: <xsl-list@lists.mulberrytech.com>
Sent: Wednesday, December 19, 2001 3:55 PM
Subject: Re: [xsl] document() merge DISTINCT


> Hi Alex,
> 
> > In each file all /person/@id are unique, but different files might
> > contain the same @id . Now I want to produce a list of all <person>
> > so that /person/@id is unique.
> 
> This is certainly more difficult than trying to find distinct values
> within a single document, because key(), preceding-sibling:: and so on
> all work within a single document.
> 
> One method, if you don't mind using an extension node-set() function,
> is to generate a single result tree fragment containing all the person
> elements, convert that to a node set, and then work with that new
> 'document' getting distinct values in the same way as you would
> normally (e.g. with the Muenchian method).
> 
> That method has disadvantages because it uses the extension function
> and because the intermediate node set that you're constructing could
> be quite large, take up memory and therefore lead to slower
> performance. If these don't turn out to be issues, though, it's the
> method that I'd choose because it's easy.
> 
> The alternative is to use a recursive method. I'd write a template
> that takes two arguments: a node set of unique people and a node set
> of remaining people:
> 
> <xsl:template name="distinct">
>   <xsl:param name="unique" select="/.." />
>   <xsl:param name="remaining" select="/.." />
>   ...
> </xsl:template>
> 
> Then work through the remaining people one by one by recursion. If
> there are people remaining, look at the first one to see whether it
> should be added to the unique list (its id isn't the same as an
> existing unique person) or not, and call the template with the new
> sets:
> 
> <xsl:template name="distinct">
>   <xsl:param name="unique" select="/.." />
>   <xsl:param name="remaining" select="/.." />
>   <xsl:choose>
>     <xsl:when test="$remaining">
>       <xsl:call-template name="distinct">
>         <xsl:with-param name="unique"
>           select="$unique | $remaining[1][not(@id = $unique/@id)]" />
>         <xsl:with-param name="remaining"
>                         select="$remaining[position() > 1]" />
>       </xsl:call-template>
>     </xsl:when>
>     <xsl:otherwise>
>       ...
>     </xsl:otherwise>
>   </xsl:choose>
> </xsl:template>
> 
> If there are no people remaining, then you need to do whatever you
> want to do to the unique people - apply templates to them for example:
> 
> <xsl:template name="distinct">
>   <xsl:param name="unique" select="/.." />
>   <xsl:param name="remaining" select="/.." />
>   <xsl:choose>
>     <xsl:when test="$remaining">
>       <xsl:call-template name="distinct">
>         <xsl:with-param name="unique"
>           select="$unique | $remaining[1][not(@id = $unique/@id)]" />
>         <xsl:with-param name="remaining"
>                         select="$remaining[position() > 1]" />
>       </xsl:call-template>
>     </xsl:when>
>     <xsl:otherwise>
>       <xsl:apply-templates select="$unique" />
>     </xsl:otherwise>
>   </xsl:choose>
> </xsl:template>
> 
> When you call the template, I'd start off with $unique being set to
> all the person elements in your first file, since you know that they
> all have unique IDs. That will save some work. Something like:
> 
>   <xsl:call-template name="distinct">
>     <xsl:with-param name="unique"
>       select="document('sample1.xml')/project/person" />
>     <xsl:with-param name="remaining"
>       select="document('sample2.xml')/project/person" />
>   </xsl:call-template>
> 
> The expression for $remaining could include more documents, naturally.
>   
> I hope that helps,
> 
> Jeni
> 
> ---
> Jeni Tennison
> http://www.jenitennison.com/
> 
> 


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