[xquery-talk] Construct the absolute xpath (with node position)

Michael Kay mike at saxonica.com
Wed Jun 18 11:40:40 PDT 2008

> ! That's interesting...  I guess it makes a lot of XQuery 
> technically non-portable.
> Are there any processors which don't support them?

I seem to remember we had a last-ditch attempt to make support for all the
axes mandatory before going to CR, on the grounds that they were so widely
supported (and widely needed!); but one or two of the RDBMS vendors held out
against it. And when I last looked at DB2, for example, the reverse axes
weren't supported.

Personally, I have always felt the arguments for not supporting the full set
of axes were spurious. The arguments that say they aren't needed just betray
ignorance. The arguments that say it's difficult or inefficient to support
them can easily be countered by showing (a) that expressions using the
optional axes can be automatically rewritten into expressions that don't use
them, and (b) the constructs that users have to write to work around the
absence of these axes are far harder to optimize than if the users were able
to express their needs more directly.

Michael Kay

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