RE: Call for feedback : Update extensions

> The basic update statement I suggest (to update the source DOM) is :
> 
>   <xslql:update
>     match = pattern 
>     select = expression>
>   <!-- Content: template -->
>   </xslql:template> 
> 
Match=pattern suggests you have to search the whole document looking for the
nodes that match, which is pretty inefficient.

SAXON only allows update of attributes on the current (element) node, and
uses the syntax 
<saxon:set-attribute name="attname"
[select="expr"]>[value]</saxon:set-attribute>
If you want to do update multiple nodes, or update a node that is not
current, you use xsl:for-each, e.g
<xsl:for-each select="//item[not(@price)]">
<saxon:set-attribute name="price" select="100.00"/>
</xsl:for-each>
It would be easy to extend this syntax to modify the value of a text node;
other updates such as adding or deleting nodes would require more careful
thought, not only as regards the syntax, but also as regards the
side-effects, e.g. on the value of variables that hold a node-set. Generally
speaking, updating the source tree rather violates the spirit of the
language. The main reason I implemented saxon:set-attribute was part of the
attempt to create a version of XSL that worked without building the full
tree in memory, though it can also be very handy for expanding defaults e.g.
before doing totalling or sorting. I have mixed feelings on whether it was a
good idea.

Mike Kay


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