RE: [xsl] Transform XML to XML

[JBryant@xxxxxxxxx]

> I'm still confused by ".", "*", "node()", etc.  I've read all
> the definitions, but somehow I can't grok them.  Any thoughts?

> -Mike

Hi, Mike,

It helps a lot to remember the idea of context. "." refers to the current 
context node. "*" refers to all the children of the current context node. 
So the basic idea is: first set the context, then select something 
relative to that context.

So, if I have a baby XML document like this:

<foods>
  <fruits>
    <apple>apple</apple>
    <banana>banana</banana>
    <cherry>cherry</cherry>
  </fruit>
  <vegetables>
    <asparagus>asparagus</asparagus>
    <brocolli>brocolli</brocolli>
    <cauliflower>cauliflower</cauliflower>
  </vegetables>
</foods>

Then I can set the context in a number of ways, as shown in the following 
stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>

<xsl:output method="xml" indent="yes"/>

  <xsl:template match="/">
    <test_out>
      <xsl:apply-templates/>
    </test_out>
  </xsl:template>

  <xsl:template match="fruits">
    <!-- now the context is the fruits node -->
    <xsl:apply-templates/>
    <xsl:for-each select="/foods/vegetables">
      <!-- now the context is the vegetables node -->
      <xsl:apply-templates select="preceding-sibling::fruits/*"/>
      <!-- I'm going to process fruit nodes even though the context is 
vegetables -->
    </xsl:for-each>
  </xsl:template>

  <xsl:template match="apple|banana|cherry">
    <!-- now the context is an individual fruit -->
    <fruit_out><xsl:value-of select="."/></fruit_out>
  </xsl:template>

  <xsl:template match="vegetables"/>

</xsl:stylesheet>

The result is:

<?xml version="1.0" encoding="UTF-8"?>
<test_out>
  <fruit_out>apple</fruit_out>
  <fruit_out>banana</fruit_out>
  <fruit_out>cherry</fruit_out>
  <fruit_out>apple</fruit_out>
  <fruit_out>banana</fruit_out>
  <fruit_out>cherry</fruit_out>
</test_out>

So thinking about context and about how you can get from the current 
context to the bit of data you want helps a big bunch.

(Hopefully, I didn't muddy the waters more than I clarified them for you.)

Jay Bryant
Bryant Communication Services
(presently consulting at Synergistic Solution Technologies)