Re: [xsl] Having Trouble With Condition For Default Nodeset Selection

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2006-07-05 10:49 +1000, Duncan Anker wrote:
> On the use of "//",  the $currency-data comes
> from a select="document(..)"  and so seems to be
> required or I get no result set - although I can
> probably fold the currency-data and codes into a
> single select. Better pass me that mallet again. :)

When I teach my XSLT class I tell my students "if
you think you need //, think again because you
probably don't" because the use of "//" is the
biggest unnecessary hit on XSLT processing
*unless you really need to search each and every
descendent down each and every subtree of the
source node tree from the point where "//" is used*.

Note my emphasis.  I'm not saying it is evil ...
sometimes you really do need to search each and
every descendent ... but often you do not.  Many
new users of XSLT liberally use "//" thinking
that it will somehow stop at the items they are
looking for, not realizing that it goes below
anything it finds looking all the way to every
leave of every subtree looking for more of what is being looked for.

Perhaps you need something like "document(..)/*/codes".

For example, in UBL we are using code lists
expressed in genericode[1] and something like
"document(..)/*/SimpleCodeList/Row[Value/SimpleValue=$code]"
would be more efficient and less wasteful than
"document(..)//Row[Value/SimpleValue=$code]".

I hope this helps.

. . . . . . . Ken

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