> >>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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