Hi,

I am struggling to try and understand what this xslt is doing and would appreciate some help in understand its logic.

Here is the XML:
________________

<?xml version="1.0"?>
<Label ID="gb03spp" xmlns="">
  <C CR="RADIO" CID="555" CPID="48" CC="39">
    <S SR="RADIO SHOWS" SID="5419" SPID="555" SC="7">
      <T TR=" " TID="12101" TPID="5419" TRID="TTTTTTTT" TC="1">
        <Q QR="Pepsi Network Chart Show" QID="75928" QPID="12101" QC="0">
          <A AR="I Specially Choose To Listen To It" AID="766804" APID="75928" AC="5"/>
          <A AR="I Listen To It Only Because Someone Else Likes It" AID="766805" APID="75928" AC="5"/>
        </Q>
        <Q QR="I Specially Choose To Listen To It" QID="75963" QPID="12101" QC="0">
          <A AR="Pepsi Network Chart Show" AID="766993" APID="75963" AC="49"/>
        </Q>
      </T>
    </S>
  </C>
  <C CR="TELEVISION VIEWING" CID="556" CPID="48" CC="39">
    <S SR="TELEVISION PROGRAMMES" SID="5426" SPID="556" SC="7">
      <T TR="TV Programmes" TID="12118" TPID="5426" TRID="TTTTTTTT" TC="1">
        <Q QR="The Pepsi Chart (January-September 2002)" QID="76158" QPID="12118" QC="0">
          <A AR="I Specially Choose To Watch It" AID="768561" APID="76158" AC="5"/>
        </Q>
      </T>
    </S>
  </C>
  </Label>


XSLT
____

<xsl:template match="/" >
    <div class="show">
      <xsl:call-template name="h">
        <xsl:with-param name="path">
          <xsl:value-of select="/Label/@dirroot" />
        </xsl:with-param>
      </xsl:call-template>
    </div>
  </xsl:template>

From the root, we call templates and pass the $path parameter. As you can see in the XML above, there is no /Label/@dirroot attribute in the xml - <xsl:value-of select="/Label/@dirroot" />. So in the dubugger I see $path {Dimension:[1]} [1]{Children:[0]}

<xsl:template name="h" match="/Label" >
    <xsl:param name="path" />
    <div class="show">
      <xsl:attribute name="id">
        <xsl:value-of select="@HeaderID" />
      </xsl:attribute>
      <xsl:attribute name="hfs">
        <xsl:if test="following-sibling::*">true</xsl:if>
      </xsl:attribute>
      <xsl:apply-templates>
        <xsl:with-param name="path">
          <xsl:value-of select="$path" />\<xsl:value-of select="@name" />
        </xsl:with-param>
      </xsl:apply-templates>
    </div>
  </xsl:template>

Here we recursively apply template and path will look like this:

$path {Dimension:[1]} [1]{Children:[1]}child::node()[1] \
What are the two double slashes? How did they appear here? \
We call template again and this time we go to the C template. Inside the C template $path looks like this:

$path {Dimension:[1]} [1]{Children:[1]}child::node()[1] \\\
So it seems that it keeps increment the number of back slashes from \\ to \\\\ and so on.


<xsl:template match="C" >
    <xsl:param name="path" />
    some contente...
    <xsl:apply-templates>
      <xsl:with-param name="path">
        <xsl:value-of select="$path" />\<xsl:value-of select="@name" />
      </xsl:with-param>
    </xsl:apply-templates>
  </div>
</xsl:template>

I would appreciate if someone could help me to understand what is going on here. Is this a common technique used in xslt to build trees where you have a hierarchy? I do not undertand the job of the $path parameters. What are those back slashes \\\\?

Cheers

C

Well, I can't tell why the stylesheet is selecting an attribute that doesn't exist. But given that it does so, it's fairly obvious why it's behaving the way that it does. The backslash characters come from this:

<xsl:value-of select="$path" />\<xsl:value-of select="@name" />

If both $path and @name are empty, then all you are left with is the "\" in between; next time through it adds another "\", and so on.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Hi Michael,

Thanks for the reply.

So this might be a technique to work with a hierarchy? Maybe the backslash tells the position we are on in the hierarchy?

The xslt works fine but why someone would use an empty value for a parameter like that? It is mind boggling.

Cheers

C

>why someone would use an empty value for a parameter like that?

I'm a programmer, not an archeologist. When I see something like this I tend to assume that it was code that did something useful at the time but has been overtaken by events.


Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference