Re: RE: Muenchian technique, was (Keys on multiple el

Hi Dave,

>> So in general if you're trying to assess whether two nodes are the
>> same, it's important to pull out the two nodes individually. The
>> only reason that you can get away with *not* using the [1] if
>> you're using the generate-id() method of comparing nodes is because
>> generate-id() automatically looks at only the first node in the
>> node set.
>
> Am I right in thinking that 'the first node in the node-set' in the
> para above, means the first node for which the predicate is true?

No, I meant the first node in the node set passed as the argument to
the generate-id() function. In other words:

  generate-id($node-set)

is exactly the same as:

  generate-id($node-set[1])

When you the node set you pass to generate-id() contains more than one
node, it returns a generated ID for the first node (in document order)
in the node set.

> I had this last week with 
>
> $variable[generate-id(.) = generate-id(key('rows', name)[1])]
>
> so here the ndl in $variable is 'searched' for the first node for
> which the predicate is true? Then returned as the value of the
> expression?

Obviously it depends on the data, but the above expression should
return more than one node in some circumstances - all those nodes in
the $variable node set that are the first node (in document order)
returned by calling the key with their name element child as the key
value. So $variable is searched for *all* nodes for which the
predicate [generate-id(.) = generate-id(key('rows', name)[1])] is
true.

If you only got one node back from the above expression as a whole
then perhaps all the nodes in the $variable node set have the same
name, or those that have a different name weren't indexed by the
'rows' key, or you were using it in a context where the result of the
above expression got converted to a node set containing only one node
(e.g. in xsl:value-of, as an argument to string() or number(), or of
course generate-id() ;).

Hope that makes sense (bit worried we're starting to talk at cross
purposes).

Cheers,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/


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