Re: [xsl] The identity transform and attributes

[Abel Braaksma <abel.online@xxxxxxxxx>]

Andrew Welch wrote:
> On 21/01/2008, David Carlisle <davidc@xxxxxxxxx> wrote:
>   
> > > It's certainly not intuitive that when you what to just change the
> > > attribute's value you have to create a new attribute node
> > >       
> > Intuition is a personal thing but I don't see why that's not
> > intuitive. xslt never updates nodes in place, so you always generate new
> > nodes.
> >     
>
> Sure, but I meant along the lines of copy vs create... To update an
> element's "value" you tend to copy it rather than create a new one.
> To update an attribute's value I would say it's intuitive to try the
> same approach, especially when the name and value are clearly separate
> (to me!).
>   

My intuition is the same as yours ;) I understand the reasoning behind 
the decisions, but I find myself doing a lot of extra work when I am 
dealing with attributes. I always have to remind myself whether it is an 
attribute node or an element node. Funnily enough, I don't have that 
same problem with text nodes or document nodes, somehow I find them 
(though different) more "intuitive".

> > Attributes are leaf nodes and work the same way as namespace nodes, and
> > PI nodes (that is they have a name and value but no children) element
> > nodes are the only ones to have name and children, document nodes have
> > children but no name, and comments and text nodes have a value but no
> > name.
> >     
>
> I've been caught out before doing things like:
>
> <xsl:template match="@*[not(self::foo)]">
>
> ...which doesn't work - you have to use name()
>   

or the following (not tested), which has the advantage of not using 
unschema-aware strings:

  <xsl:template match="@*[not(../@foo is .)]

but that's hardly clearer

> Again, I don't know why the self axis isn't available for attribute
> nodes... any ideas?

Not 100% certain here, but I vaguely remember that self:: only works on 
elements and document nodes, not on other node types (i.e., a text node 
does not have a self:: axis, nor does a PI or a comment) . And an 
attribute's self:: axis would naturally be an attribute axis, which 
cannot hold.

Cheers,
-- Abel --