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RE: Purpose of generate-id index [1]

2003-06-25 01:23:20
In general terms why is the [1] index present.

As you noticed, it is redundant. Two reasons why it is still 
commonly used: 1. Make it explicit to human readers that the 
first element
   of the node set returned by key() is used. Not everybody
   has always all details of the spec at hand.
2. Moderatly clever processors might take the index as a clue
   not to construct the whole node set, which can save time and
   memory. Really clever processors could take the same clue
   from the presence of the generate-id() function of course,
   but the former is still a bit easier to implement and also
   more worth to do because the optimization is also an improvement
   in many more situations.


A third reason, better than either of these: when you move to XSLT 2.0,
and switch off "backwards compatibility" mode, it will become an error
to supply a sequence of nodes to a function that's designed to handle
only one. So if you really want to process just the first node, you have
to say so.

Michael Kay



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