- From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
- Date: 01 May 2002 20:26:43 +0100
- To: Jeni Tennison <jeni@jenitennison.com>
- Cc: "Morris Matsa" <mmatsa@us.ibm.com>, Yuri de Wit <yuri.dewit@metaserver.com>, "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>
Jeni Tennison <jeni@jenitennison.com> writes: > Hi Morris, > > > I believe that necessarily infinitely recursive unsatisfiable types > > are forbidden in Schemas. This question was answered about a year > > ago on this list [1], and the part of the schema spec quoted then > > was [2]. Please tell me if I'm wrong. > > Hmm... I don't think that the definition of an emptiable group > (http://www.w3.org/TR/xmlschema-1/#cos-group-emptiable) relates to the > question of infinitely recursive unsatisfiable types. As far as I can > tell, the only places in which this Schema Component Constraint is > used is when assessing whether it's OK to derive one type from another > type, and whether an element's default/fixed value is OK. > > There might be something else specifying a constraint like this > somewhere, of course, but I don't think that's it. If there were such > a constraint, I guess it would be a constraint on model groups that > stated that a model group whose minimum effective total range is more > than 0 cannot contain an element particle at any level whose minimum > effective total range is more than 0 and whose type's content involves > that model group at any level. But I can't see such a constraint > anywhere. There isn't one. It would be very expensive to enforce, and not in at least my judgement worth it. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2002, part-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk URL: http://www.ltg.ed.ac.uk/~ht/ [mail really from me _always_ has this .sig -- mail without it is forged spam]
Received on Wednesday, 1 May 2002 15:26:57 UTC