Re: Why not reinvent the wheel?

[Joe English <jenglish@flightlab.com>]

Jonathan Robie wrote:
> Joe English wrote:
> >I wouldn't go that far either; the structure of XQuery does look
> >to me like it's more amenable to optimization than XSLT.
> >But the '..' axis is definitely problematic.
> [...]
> Now the question - if a user chooses to write recursive functions to do
> this sort of thing, does that user have the right to expect that we will
> optimize such queries well?

I think that '..' may turn out to be one of those features
that you have to pay for even if you don't use it.
Since an XQuery engine _might_ need to evaluate '..',
it rules out many implementation strategies that would be
more space-efficient than those used by conventional XSLT
processors.

It will be interesting to see what XQuery implementors
come up with though.  I have a hard time envisioning a
space-efficient query evaluation framework which also
supports '..', but that's no doubt due to a lack of
imagination on my part.  (OTOH, I can think of several
that don't or can't support '..'.)

I also notice that none of the example queries in the WD,
and only one in the "Use Cases" document, require '..'.
Is this feature really essential for XQuery?


--Joe English

  jenglish@flightlab.com