RE: external functions in xquery

And obviously, if a vendor introduces side-effects that do not work with
a declarative processing, he has to take extra care to not make his
XQuery implementation instable...

 

Best regards

Michael

 

________________________________

From: www-ql-request@w3.org [mailto:www-ql-request@w3.org] On Behalf Of
Kay, Michael
Sent: Friday, December 19, 2003 9:16 AM
To: Damien Fisher; www-ql@w3.org
Subject: RE: external functions in xquery

 

External functions are only supported to the extent that the vendor
chooses to support them. It's therefore up to each vendor to say what
they support and what the restrictions are.

 

Michael Kay

	-----Original Message-----
	From: www-ql-request@w3.org [mailto:www-ql-request@w3.org] On
Behalf Of Damien Fisher
	Sent: 19 December 2003 09:33
	To: www-ql@w3.org
	Subject: external functions in xquery

	Are there any limits imposed on external functions in XQuery?
E.g., can external functions have side-effects which might affect
documents referenced in the query, in which case evaluation order is
important?  Must the value returned by an external function for a given
set of parameters be independent of when that function call is made, or
the number of such function calls?

	 

	(I notice there is an editorial note in the current formal
semantics draft which might cover these questions, which references
"Issue 522 (FS-Issue-0179)".)

	 

	Similarly, for external variable declarations, must the value of
the variable remain constant?  I personally think this is a reasonable
restriction.

	 

	In my opinion, keeping XQuery purely declarative would be an
important goal, and so I hope that the restrictions on external
functions and variables would reflect that.