On Mon, May 07, 2007 at 09:35:37AM +0200, Jens Teubner wrote:
On Sun, May 06, 2007 at 10:28:57PM +0200, Ying Zhang wrote:
If I run the follwoing XQuery query with Galax:
========== test.xq ========== declare namespace t = "test";
declare function t:echoVoid() { () }; t:echoVoid() ==========
Galax gives a warning:
$ galax-run ~/test.xq [WARNING] Expression '???' at File "/ufs/zhang/test.xq", line 3, characters 8-37 has empty type, but is not the empty expression
Jennie,
it is a static type error when expressions can statically be determined to return the empty sequence. The XQuery Formal Semantics allows such empty sequences only in very rare cases (e.g., as the argument of a function call). This is why Galax complains. Pathfinder's type checker, unfortunately, is not smart enough to detect these kind of things and does not complain.
Hi Jens, Thanks for the explanation. So I think I will have to live with this warning :( Jennie
The rationale behind the behavior as specified in the specs is that an XQuery processor could detect typos in the user input query, e.g., if a user mis-types tag names in XPath location steps. A fully schema-aware system might be able to detect such things.
Jens
-- Jens Teubner Technische Universitaet Muenchen, Department of Informatics D-85748 Garching, Germany Tel: +49 89 289-17259 Fax: +49 89 289-17263
Things are pretty mixed up, but I think the worst is over. -- TeX Error Message
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