Normative DTD [was: Re: Possible schema validation issue in 3.0b3]

I'm changing the subject title to focus on just the "normative DTD"
aspect, and replying only to xml-schema-comments on this topic.

Dan Connolly wrote:
> 
> "Falk, Alexander" wrote:
> >
> > This message is a question concerning the use of entities to emulate
> > namespace prefixes in a DTD - a technique that is being used by the
> > normative DTD from the April 7 XML Schema draft.
> 
> Hmm... I thought the DTD was informative...
> making it normative seems to conflict with the use
> of anyAttributes...
> 
>    "<complexType name="openAttrs" content="empty">
>             <annotation>
>              <documentation>This type is extended by almost all schema
> types
>                             to allow attributes from other namespaces to
> be
>                             added to user schemas.</documentation>
>             </annotation>
>             <anyAttribute namespace="##other"/>
>            </complexType>
>    "
>    -- http://www.w3.org/TR/2000/WD-xmlschema-2-20000407/#schema
> 
> but there it is:
> 
> "B (normative) DTD for Schemas"
> http://www.w3.org/TR/2000/WD-xmlschema-1-20000407/#normative-schemaDTD
> 
> I don't see any prose that actually says "an XML schema must
> match the DTD in appendix B", though. Odd.

I was thinking about this the other day, and here is the closest
approximation I found:

"4.3 XML Representation of Schema Components

For each kind of schema component there is a corresponding normative XML 
representation. The sections below describe the correspondences between 
the properties of each kind of schema component on the one hand and the 
properties of information items in that XML representation on the other, 
together with constraints on that representation above and beyond those 
implicit in the (normative) Schema for Schemas (§A) and (normative)
DTD for Schemas (§B)."

It sounds as though the checking of constraints "implicit" in the
normative
Schema for Schemas and DTD is required (even if the schema has been
presented
in component form rather than in an XML representation?).

What I was worrying about was the following:

1) Are processors supposed to conceptually validate a schema using both
the 
DTD and the Schema for Schemas?  Are implementors supposed to figure out
how 
to optimize this, e.g. what constraints are imposed by the DTD that are
not 
also imposed by the Schema for Schemas?  Should any such DTD-only
constraints 
be specified instead as Constraints on Schemas, so that the DTD can be
made 
non-normative, and serve as just a useful approximate guide for people
(like 
me) who like reading DTD syntax?

2) Are constraints stated in comments in the DTD taken to be normative,
e.g.

"<!ATTLIST %element;
              
   ...
         <!-- maxOccurs defaults to 1 or minOccurs, whichever is greater
-->"

which was of recent interest because it conflicted with a rule
elsewhere.

Thanks,

  David

Received on Monday, 12 June 2000 19:38:31 UTC