Re: Notation Declaration Schema Component

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
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