Re: [xsl] Identical entries in different input documents should appear in the output document only once

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2007-09-07 17:54 +0200, Meyer, Roland 1. (NSN - DE/Germany - MiniMD) wrote:
> I have the following problem. I have a couple of XML documents to merge
> to one output document.
> Each document has the same structure like this:
>
> <root>
>   <block>
>     <oneTag>some value<oneTag>
>     <anotherTag>another value<anotherTag>
>      ...
>     <idTag>setId-itemId<idTag>
>   </block>
>   <block>
>      ...
>   </block>
>    ...
> </root>
>
> I have to interpret the value in the idTag (the setId-itemId) as an
> identifier for the complete structure between the block tags.
> Within one document this identifying value comes only once, but the same
> identifying value can be found in different documents.
>
> What I now need:
> My output file should list each block only ones, means although the same
> identifying value is present in different input documents, it should
> appear only once in the output document.
>
> I can think about some heavy procedures by checking every found
> identifier value in the already processed files (because then they are
> already written to the output), but this will be very time consuming (I
> have around 15 files with each up to 10000 blocks).
>
> Is there any other and simpler way to - let's say - memorize the already
> written blocks resp. identifiers?

Mike is correct that the variable-based grouping method would work 
with this, but it is far slower than an XSLT 2 approach.  When using 
XSLT 1.0 I find variable-based grouping acceptable for sub-document 
and multi-document grouping.

The code would work along the lines of the following, and it assumes 
that there is an XML structure $files with the list of all the file names:

  <xsl:variable name="items"
                select="document($files/file/@uri,.)/root/block"/>
  <xsl:for-each select="$items">
     <!--walk through all, doing work at first of each unique idTag-->
     <xsl:if test="generate-id(.)=
                   generate-id($items[idTag=current()/idTag])">
        <!--the following executes once for each unique idTag
            value across all the files-->
     </xsl:if>
  </xsl:for-each>

I hope this helps.

. . . . . . . . . . . . . Ken

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