- From: Henry S. Thompson <ht@inf.ed.ac.uk>
- Date: Tue, 10 May 2005 09:31:28 +0100
- To: Alain Frisch <Alain.Frisch@inria.fr>
- Cc: www-xml-schema-comments@w3.org
Alain Frisch writes: > ============================================================== > {system identifier} > Optional if {public identifier} is present. A URI reference. > {public identifier} > Optional if {system identifier} is present. A public identifier, > as defined in [XML 1.0 (Second Edition)]. > ============================================================== > > which means that in the Schema document model, at least one of > the two identifiers must be present. > > But there is no formal constraint to ensure that in the XML > representation of XML Schema, neither in the text of the > recommendation nor in the Schema for Schema. This is a general principle -- if the _components_ are constrained, then we don't redundantly state a constraint on the XML representation. XML representations are only allowed which represent valid components [1]: "*Schema Representation Constraint: Notation Definition Representation OK* In addition to the conditions imposed on <notation> element information items by the schema for schemas, the corresponding notation definition must satisfy the conditions set out in Constraints on Notation Declaration Schema Components (3.12.6)." > ============================================================== > {system identifier} The ·actual value· of the system [attribute], > if present, otherwise ·absent·. > {public identifier} The ·actual value· of the public [attribute] > ============================================================== > > which doesn't allow the public identifier to be missing. Well, it doesn't say clearly what to do if it is. > I guess there is missing "if present, otherwise ·absent·.". Yes, we should add that, thanks. ht [1] http://www.w3.org/TR/xmlschema-1/#src-notation -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh Half-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@inf.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 Tuesday, 10 May 2005 08:31:34 UTC