Re: [xsl] Delete element except one child

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

At 2006-05-12 00:11 -0700, Hind Al-Hakami wrote:
> How can I do the following:
> If "UML:Package" has "xmi.idref" attribute then delete
> its grand-Pa element bolck. Otherwise
> delete "UML:Package" element except the children of
> its child element "UML:Namespase.ownedElement"
> ...
> XSLT Code:
>         <xsl:template match="*[name(descendant::*[2]) =
> 'UML:Package']">
>                 <xsl:choose>
>                         <xsl:when
> test="string-length(descendant::UML:Package/@xmi.idref)
> &gt; 0"/>
>                 </xsl:choose>
>         </xsl:template>

A few things about the above:

(1) the predicate "[2]" will check the second of all of the 
descendants *in document order*, not in depth, so the test of 
"grandchildren" would be done directly with XPath steps
(2) it is unsafe and bad practice to check the names of 
namespace-qualified information items because that incorporates the 
use of an arbitrary prefix which may not match the input
(3) you have not written a test that would keep the element even if 
there is no attribute on the grandchild ... your template rule 
removes the element regardless of whether there is an attribute or not
(4) an attribute's presence is not best checked by checking its 
string length; it is sufficient merely to address the attribute node 
and the predicate will be false if the attribute is absent

I would rewrite your above statement, though I do not have time to 
work with your test data, as:

  <xsl:template match="*[*/UML:Package/@xmi.idref]"/>

You should also review the appropriateness of using "//" where you 
have, as that is a big hit against performance and a common 
inappropriate use of XPath by new users of XSLT.

I hope this helps.

. . . . . . Ken

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