Re: XSL Working draft question

size[attribute(width)] returns the "size" child elements that have an
attribute named width; size/attribute(width) returns the "width"
attributes of the "size" child elements.

Here's how I think of it.

A query is an expression that takes an input set of nodes and returns
another set of nodes.  For a select pattern, the input node set is the
current node.  For a match pattern, the input node set is the entire
set of nodes in the source document and the pattern matches a node if
the node is a member of the result of the query.

A query of the form "foo" returns the "foo" child elements of the
nodes in the input node set.

A query of the form "attribute(foo)" returns the "foo" attributes of the
nodes in the input node set.

The "/" operator does composition. It takes the input node set and
applies the left operand to yield another set of nodes; it then uses
than as the input set of nodes to the right hand operand; the result
of this is the result of the "/" expression.

Square brackets do selection. An expression of the form e[b] evaluates
b returning a result X and for each node in X evaluates b; it returns
the set of nodes from X for which b evaluates to true. b is a boolean
expression which is an expression that takes an input set of nodes and
returns true or false.  Any query can be used as a boolean expression
and will evaluate to true if it returns an empty node set.

The draft is rather less general than this (for example, it restricts
the queries that can be used in boolean expressions within square
brackets), but you may find it easier to understand if you think of it
in more general terms.

James

Jeremy CALLES wrote:
> 
> In the 2.7.11.3 paragraph of the XSL WD, Attribute Value Templates is
> explain.
> 
> But in the example
> 
> <xsl:define-constant name="image-dir" value="/images"/>
> 
> <xsl:template match="photograph">
> <IMG SRC="{constant(image-dir)}/{href}"
> WIDTH="{size/attribute(width)}"/>
> </xsl:template>
> 
> With this source
> 
> <photograph>
>   <href>headquarters.jpg</href>
>   <size width="300"/>
> </photograph>
> 
> I don't understand this match: size/attribute(width)
> Normally an attribute should be matched by the command
> size[attribute(width)],
> according to the 2.6.8 paragraph.
> 
> Is it a typo or a new mean of matching attributes especially for
> Attribute Value Templates.
> 
> Thanks
> --
> Jeremy CALLES  --- jcalles@xxxxxxxxxx
> home page      --- http://www.mygale.org/07/jcalles
> 
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