RE: [xsl] Manipulating elements depending on the existence of sub-elements

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

At 11:01 AM 3/12/2008, it was written:
> Try something like this:
>
> <xsl:template match="/"
>   <xsl:apply-templates select="//UniqueInfo"/>
> </xsl:template>
>
> <xsl:template match="UniqueInfo">
>   <transaction>
>     <xsl:apply-templates
> select="../preceding-sibling::transaction[not(UniqueInfo)]/line | ../line"/>
>   </transaction>
> </xsl:template>

This is nearly there, but won't it break when the second group of 
transactions appears without a UniqueInfo?

As in

<Transaction which="A">
  <Line>...</Line>
  <Line>...</Line>
</Transaction>
<Transaction which="B">
  <Line>...</Line>
  <Line>...</Line>
</Transaction>
<Transaction which="C">
  <Line>...</Line>
  <Line>...</Line>
  <UniqueInfo>...</UniqueInfo>
</Transaction>
<Transaction which="D">
  <Line>...</Line>
  <Line>...</Line>
</Transaction>
<Transaction which="E">
  <Line>...</Line>
  <Line>...</Line>
  <UniqueInfo>...</UniqueInfo>
</Transaction>

... it would work for Lines belonging to C, but Transaction E would 
get A and B along with D and E.

To fix this, one could use a key to select all the Lines that belong 
to any given UniqueInfo:

<xsl:key name="Lines-for-UniqueInfo" match="Line"
   use="generate-id((../UniqueInfo | 
../following-sibling::*/UniqueInfo)[1])"/>

and then

<xsl:template match="UniqueInfo">
  <transaction>
    <xsl:apply-templates
      select="key('Lines-for-UniqueInfo',generate-id())"/>
  </transaction>
</xsl:template>

... and then position() gives you the number as above.

> Alternatively, what I often advise people when handling dirty data: write
> two transformations and run them in series (a pipeline). The first one is to
> clean up the data, the second is to transform it. One benefit is that when
> you fix the data supplier to stop generating dirty data, you can throw out
> the first stylesheet. Another benefit is that the clean-up stylesheet will
> be reusable when you want to process the dirty data in a different way.

Definitely.

Cheers,
Wendell


======================================================================
Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
17 West Jefferson Street                    Direct Phone: 301/315-9635
Suite 207                                          Phone: 301/315-9631
Rockville, MD  20850                                 Fax: 301/315-8285
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