[dsdl-comment] Re: Come On, DTD, Come On! Thoughts on DSDL Part 9

(I have split the response into two separate emails so as to not
cross-post; this is the answer to the DSDL-Comment mail list)

At 2002-06-11 13:31 -0400, John Cowan wrote:
>ISO/IEC 19757-9 is currently an empty hole titled "Datatype- and
>namespace-aware DTDs". This is a ragbag of ideas to fill that hole.

Thanks again, John, for the contribution!

If I were to distill the use-cases from your suggestions:

Namespaces:

>1) The NS declaration ...
>to define the namespaces associated with CNames in ELEMENT
>and ATTLIST declarations. As is the case for other schema languages, in
>the presence of a known prefix, name matching is done on the universal
>name (URI + local-part) rather than the CName. The default namespace
>is declared using #DEFAULT in place of the name.
>...
>Issue: Is it an error to mention a prefix that is not declared? My
>answer: no; if this is done, name matching falls back to string identity.
>..
>Issue: this does not help when prefixes are not used consistently
>throughout an instance. Do we care? My answer: no.

Datatypes:

Attributes:

>2) Attribute data types. The names that can appear in an ATTLIST
>declaration [need to be associated with] ...
>the datatype names of part 5 (i.e. XSD simple types).
>...
>Issue: do we need to make the datatype list extensible? If so, we could
>use QNames and a DATATYPE declaration, rather like the compact syntax
>of RELAX NG.

Elements:

>3) Element simple datatypes. Likewise, ...
>ELEMENT declarations are extended from just ANY and EMPTY to include
>these same datatypes.

Lists of datatypes:

>4) Datatype lists. In either #2 or #3 context, [one needs] ...
>to indicate a ...
>list of strings matching the datatype.

Choice of datatypes:

>5) Datatype choice. In either #2 or #3 context, a simple or [list of]
>datatype name can be replaced ... to indicate a choice
>(derivation by union in WXS terms).
>...
>Issue: what do we do about XSD facets? They are important

Content models:

>6) Restore & connector. Bring back the & connector, either with the
>SGML semantics (A,B)|(B,A), or preferably with the RELAX NG "interleave"
>semantics. The difference is that, given the content model "A & B+",
>the element sequences A, B, B, B and B, B, B, A will match in either case,
>but B, A, B, B will only match using interleave semantics.
>
>Issue: SGML or interleave? My answer: interleave

Ambiguity:

>7) Abandon SGML 1-ambiguity rules. Instead, allow complete flexibility of
>content models. See James Clark's discussion in "The Design of RELAX NG".

Model groups:

>8) Restore multiple element and attribute names separated by |s.
>This makes for conciseness and easy authoring.

Element terminal content:

>9) Fixed element content. Allow ELEMENT declarations to specify [a fixed
>value, possibly of a given datatype]

Document element validity declaration:

>General issue: Should there be some way to indicate candidate roots?
>In existing DTDs, any element can be a root.

Declaration subset processing:

>General issue: We need to figure out what to do if the instance contains
>an internal DTD (by which I mean an internal subset, a reference to an
>external subset, or both). Should internal validation be required,
>permitted, or forbidden when doing external validation? (I take it
>for granted that if it is to be done, it will be done in the parser,
>i.e. first.) What is the effect of attribute defaulting specified by
>the internal DTD on the external validation process? internal validation
>be done before external validation or turned off

John, I haven't thrown away your suggestions for syntactic methods of
addressing the needs ... I look forward to their consideration once
requirements are determined.

Thanks again!

....................... Ken

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