[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Re: XSLT and XQuery

• To: <michael.h.kay@n...>, "'Jonathan Borden'" <jborden@m...>, "'David Carlisle'" <davidc@n...>, "'Jonathan Robie'" <jonathan.robie@s...>
• Subject: Re: XSLT and XQuery
• From: "James Clark" <jjc@j...>
• Date: Mon, 7 Jan 2002 11:05:16 +0700
• Cc: <www-xml-query-comments@w...>, <xml-dev@l...>
• References: <004801c19513$577f1cb0$465169d5@pcukmka>

> > I  would be inclined
> > to nominate some of the axes (almost everything but children and
> > descendants) as the prime things to exclude from XQuery, both
> > because they
> > are hard to optimize and hard to statically type in any sort
> > of useful way.
>
> Now I can reverse the argument: surely most of the axes are just syntactic
> sugar for a recursive function call? And using the ancestor axis (for
> example) explicitly is surely both more convenient for the user, and
easier
> to optimize, than a recursive call on a getParent() function?

I would exclude the parent axis as well as the ancestor.  It doesn't make
much sense to me to include parent, child, descendant but exclude ancestor.

> Also, I've never understood why the descendant axis is supposedly easier
to
> statically type than the ancestor axis.

Because the child axis is easier to statically type that the parent axis.
The type of an element (in the XDuce/XQuery sense) tells you the possible
attributes and children but doesn't tell you the possible parents.  Maybe
you could do a type system that would tell you about the parents as well,
but I suspect you would get a combinatorial explosion if your type system
attempts to deal with both parents and children.

James

• Follow-Ups:
  • RE: XSLT and XQuery
    • From: "Michael Kay" <michael.h.kay@n...>

• References:
  • RE: XSLT and XQuery
    • From: "Michael Kay" <michael.h.kay@n...>

• Prev by Date: Re: 2002 as the year of XML (meltdown due to patents)
• Next by Date: Re: 2002 as the year of XML (meltdown due to patents)
• Previous by thread: RE: XSLT and XQuery
• Next by thread: RE: XSLT and XQuery
• Index(es):
  • Date
  • Thread