- From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
- Date: 09 Nov 2000 10:25:41 +0000
- To: "Bob Schloss/Watson/IBM" <rschloss@us.ibm.com>
- Cc: www-xml-schema-comments@w3.org
"Bob Schloss/Watson/IBM" <rschloss@us.ibm.com> writes: > My reading of Structures "Constraints on Complex Types", > Section 5.11 http://www.w3.org/TR/2000/CR-xmlschema-1-20001024/#coss-ct > Derivation Valid (Extension) > clause 1.1.4 and particularly clause 1.1.4.1 makes me think that > the Primer Example in "Abstract Elements and Types" section 4.7 > http://www.w3.org/TR/2000/CR-xmlschema-0-20001024/#abstract > has a definition for complexType "car" which is not allowed. > > Is this a problem of me being unable to see the parsing of all the > "ands" and "ors" which are in clause 1.1.4 of > Derivation Valid (Extension) paragraphs of Section 5.11 of Structures? > > Primer example: > > <complexType name="Vehicle" abstract="true"/> > > <complexType name="Car"> > <complexContent> > <extension base="target:Vehicle"/> > </complexContent> > </complexType> > > > Structures: clause 1.1.4 of Derivation Valid (Extension) paragraphs in > section 5.11: > > Either the {content type} of the {base type definition} and the {content > type} of the complex > type definition itself must be the same simple type definition, or else > the {content type} of > the complex type definition itself must specify a particle and either > the {content type} of the > {base type definition} must be empty or > 1.1.4.1 both {content type}s must be mixed or both must be > element-only; I _think_ this is all OK. Bear in mind this is a constraint on schema components, not XML representations. So saying 'must specify a particle' is really the same as saying 'must have complex content' (as opposed to simple content). The example above satisfies all this, because per the correspondence rules for extension [1], "2.1 if the explicit content is empty, then the {content type} of the type definition resolved to by the normalized value of the base [attribute]" you'll end up with a vacuous extension, which has a content type==particle, which will itself be a valid extension, because no change at all is a valid extension. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2001, 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/
Received on Thursday, 9 November 2000 05:25:46 UTC