RE: [xsl] Reusing XPath statements (defining once and only once)

["Dr. Frank Mabry" <fmabry@xxxxxxxxxx>]

Original XSL note from: David Mitchell (on Thu, 17 Apr 2003 at 16:36:25 
-0500)

In reviewing the code I realized that the original transform should have 
failed if it ever found a "Host" element that the additions needed to be 
made to. I have added some comments to the transform's code below.

I ran the transform with instant saxon 6.5.2 using the "trace" facility. 
It complained as documented in the following:

[.... many lines of trace information have been removed here.....]
<Instruction element="xsl:apply-templates" line="34">
<Source node="/Server[1]/Service[2]/Engine[1]/Host[1]/@name" line="-1" 
	mode="*default*">
<Instruction element="xsl:template" line="11">
 <Instruction element="xsl:copy" line="12">
Error at xsl:copy on line 12 of file:/C:/MRIS/SAXONN~1/identity2.xsl:
 Cannot write an attribute when there is no open start tag
Transformation failed: Run-time errors were reported

The transform (with comments) as provided to the XSLT list originally:


<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<xsl:output indent="yes" />
<xsl:template
	 match="@* | * | comment() | processing-instruction() | text()">
  <xsl:copy>  <!-- this is line 12 in my version -->
    <xsl:apply-templates
    select="@* | * | comment() | processing-instruction() | text()" />
  </xsl:copy>
</xsl:template>

<xsl:template match="Host">
  <xsl:copy>
    <xsl:apply-templates select="@*" />
       <!-- here you copy the attributes of the
       host element to the result tree.  -->
    <xsl:if test="@appBase='webapps'">
      <xsl:choose>
        <xsl:when test="Context[@path='/axis']" />
        <xsl:otherwise>
          <Context debug="0"
          docBase="c:\xml-axis-10\webapps\axis" path="/axis"
          reloadable="true" />
        </xsl:otherwise>
      </xsl:choose>
    </xsl:if>

    <xsl:apply-templates
    select="@* | * | comment() | processing-instruction() | text()" />
       <!-- the '@*' alternative in the preceding select eventually
       causes the system to attempt to add an attribute node
       to the result tree ... the attributes have already been
       placed in the output result tree -->
  </xsl:copy>
</xsl:template>
</xsl:stylesheet>


If the suggested change is made (i.e., removal of the "@*" alternative 
the transform performs as expected. I can't resist asking ...

What XSL processor were you using?

I been thinking that perhaps your XSL processor is one that allows the 
"illegal" construct but discarded the erroneous attributes later when 
the result tree was serialized.

Am I off the mark here?  Perhaps Mike can explain if Saxon's behavior is 
instead in error. (Also why the trace output does not have a matching 
start tag for the "trace" end tag?!)

I have to admit the little code snippet proved to be as interesting as a 
cross-word puzzle!

Frank


--

Dr. Frank Mabry
Dept. of EE&CS
U.S. Military Academy
West Point, New York, 10996

Work Phone: 845-938-2960
work email: df6954@xxxxxxxxxxxxxxx
home email: fmabry@xxxxxxxxxx

"The great use of life is to spend it for something that will outlast it."
- William James




--
Dr. Frank Mabry
Dept. of EE&CS
U.S. Military Academy
West Point, New York, 10996

Work Phone: 845-938-2960
work email: df6954@xxxxxxxxxxxxxxx
home email: fmabry@xxxxxxxxxx

"The great use of life is to spend it for something that will outlast it."
- William James




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