Re: [xsl] Newbie question - does the built-in template rules output the attribute node?

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Paul,

You asked this question a few days ago; catching up on the list I 
came across it, but it seems it hasn't been answered yet.

At 10:43 AM 10/13/2005, you wrote:
> Another newbie question, this time about XSL itself
> rather than xsltproc. (sorry!)

Please not to apologize!

> Quoting from XSLT for Dummies, it says:
>
> ------------------------------------8<----------------------------------
> For text and attribute nodes, a built-in template rule copies their
> text through into the result tree:
> <xsl:template match="text()|@*">
> <xsl:value-of select="."/>
> </xsl:template>
> In this rule, the match pattern returns all text nodes with text() and
> all attribute nodes with @*.
> The xsl:value-of instruction then transforms the current node to the
> result tree as text.
>
> ------------------------------------8<----------------------------------
>
> However, if I run this against a blank stylesheet:
>
> ------------------------------------8<----------------------------------
> <!-- miniscore.xml -->
> <score id="1">Text here
>    <film name="I should see this attribute">A Little Princess</film>
>    <composer>Patrick Doyle</composer>
>    <year>1995</year>
>    <grade>100</grade>
> </score>
>
> ------------------------------------8<----------------------------------
> The result is:
>
> ------------------------------------8<----------------------------------
> <?xml version="1.0" encoding="utf-8"?>Text here
> A Little Princess
> Patrick Doyle
> 1995
> 100
> ------------------------------------8<----------------------------------
>
> However, since the attribute node name is supposedly matched,
> I expected:
>
> ------------------------------------8<----------------------------------
> <?xml version="1.0" encoding="utf-8"?>Text here
> I should see this attribute
> A Little Princess
> Patrick Doyle
> 1995
> 100
> ------------------------------------8<----------------------------------
>
> Can anyone tell me where I'm wrong?

What the dummies book left out (or maybe is says it somewhere else) 
is what the built-in template rule for elements does:

<xsl:template match="*">
  <xsl:apply-templates select="child::*"/>
</xsl:template>

... with the effect of telling the processor "keep going: process 
this element's children".

The critical detail is that *attributes are not counted among an 
element's children*.

In other words, the built-in traversal, running along the child:: 
axis by default, never selects attributes, so they are never matched 
by their own built-in template.

To tweak this, try a stylesheet that has just this one template:

<xsl:template match="*">
  <xsl:apply-templates select="child::* | attribute::*"/>
</xsl:template>

you will find your attribute values appearing.

BTW select="child::* | attribute::*" can be shortened as select="*|@*".

We like to say that attributes have been disinherited; they know who 
their parents are, but their parents, when asked for their children, 
never mention them. They are definitely second-class citizens in the 
data model.

I hope that helps,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
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Suite 207                                          Phone: 301/315-9631
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