Re: [xsl] Where is 'intersect' Operator Defined in XPath 3?

["Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

> The assumption that the spec need not describe some corner cases because
> "it's obvious that the answer is [X], because nothing else would make
> sense" is philosophically and technically unsound.  But I have in fact
> heard that remark or variants of it from more than one spec editor
> (including the editor of XSLT 1.0), who could not entertain seriously
> the idea that any rational being might not see things the same way they
> did.  The results have seldom been ideal.  (Examples omitted.)
>

I remember arguing with Don Chamberlin that it was obvious that sum() applied
to an empty set should return zero (which wasn't stated in XPath 1.0). He
pointed out that in SQL it returned null; and also that in a system with
dynamic typing, there was no way of knowing whether the result should be
integer zero, double zero, float zero, or a zero-length duration. So he was
right, it doesn't go without saying.

On the other hand, we pretty well treat it as obvious that 2 + 2 is 4.

Michael Kay
Saxonica