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Re: Question about SHOULD in MT

From: Dan Connolly <connolly@w3.org>
Date: 10 Dec 2002 11:23:12 -0600
To: Pat Hayes <phayes@ai.uwf.edu>
Cc: w3c-rdfcore-wg@w3.org
Message-Id: <1039540993.5193.12581.camel@dirk>

On Tue, 2002-12-10 at 09:10, pat hayes wrote:
> >On Mon, 2002-12-09 at 18:35, pat hayes wrote:
> >>
> >>  >I'm not comfortable with the SHOULD in
> >>  >
> >>  >"A 'datatype-aware' RDF engine SHOULD be competent to recognize at
> >>  >least the rdfs:XMLLiteral datatype and the set of all the XML
> >>  >Schema primitive datatypes."
> >>  >
> >>  >insofar as XML Schema datatypes are concerned.
> >>  >
> >>  >I think the SHOULD should only be limited to rdfs:XMLLiteral.
> >>  >
> >>  >I don't believe this is an editorial issue. I don't believe that the
> >>  >WG has agreed that this expectation should be placed on datatype
> >>  >savvy applications.
> >>  >
> >>  >I propose the following rewording:
> >>  >
> >>  >"A 'datatype-aware' RDF engine SHOULD be competent to recognize at
> >>  >least the rdfs:XMLLiteral datatype. It MAY, and typically will,
> >>  >recognize other datatypes,
> >>  >such as the XML Schema built-in simple datatypes."
> >>
> >>  On reflection, I don't think we should shilly-shally with 'typically'
> >>  when using this strict language, so Ive simplified this to:
> >>
> >>  A 'datatype-aware' RDF engine SHOULD be competent to recognize at
> >>  least the built-in rdf:XMLLiteral datatype. It MAY also recognize the
> >>  set of all the XML Schema built-in datatypes.
> >>
> >>
> >>  OK??
> >
> >no; 'RDF engine' seems completely out of place.
> >Please strike all mentions of it.
> I don't see how that is possible.

[Sigh... again, no pointer to the relevant document...
I'll go hunting... in your message of
09 Dec 2002 10:59:22 -0600 you referred us to
but I can't reach that.... hmm... lemme try from another
machine... ok... I have something last
modified Tue, 10 Dec 2002 00:38:22 GMT]

It seems straightforward to me...


 make it easier to implement RDF reasoning engines which can check
 formal RDF entailment.

 make it easier to implement RDF entailment checking in software.

Strike the para that begins...

   In operational terms, in order to make use of datatyping information,
   a reasoning engine would require that the uriref of a datatype
   provides access to a process which at least can determine, for any
   character string, whether or not it is a valid lexical form for that
   datatype. ...


   A 'datatype-aware' RDF engine
   SHOULD be competent to recognize at least the built-in rdf:XMLLiteral
   datatype. It MAY also recognize the set of all the XML Schema

I'm not sure what to do with the occurence in the glossary;
if it's informative, (a) it seems harmless, but (b) the
glossary should say so, right under the heading.
If it contributes some novel technical information to
the spec, I'd much prefer that the glossary entries
had pointers to the sections where the terms
are introduced (bonus points for usage pointers too).

Hm... I see 'engine' isn't the only term that needs scrubbing...


Strike this:

Thus, the inclusion of a triple of the form

<ex:somedatatype> rdf:type rdfs:Datatype .

in an RDF graph can be understood by a datatype-aware RDF reasoner as a
claim that ex:somedatatype identifies a recognized datatype. Such
reasoners MAY post a warning or an error condition when they are unable
to access the minimal relevant datatype information. 

'regognized' is defined as a relationship between interpretations
and datatypes; there's no need to bring reasoners into
the picture.

I don't understand this bit:

While normal RDFS reasoning is valid when applied to the datatype
vocabulary, other implications which depend on the properties of the
datatype spaces may be missed, and datatype clashes or other error
conditions may be undetectable. 

if it contributes some novel information to the spec, please
supplement it with an example (and let's get that example
in the test suite). Otherwise, please strike it.

Strike this:

Although RDFS entailment rules apply robustly to such graphs,
datatype-aware RDF reasoners MAY treat a datatype violation as an error

strike this:

Although the definition of entailment means that a D-inconsistent graph
D-entails any RDF graph, datatype-aware RDF reasoners SHOULD NOT publish
'trivial' conclusions derived from a recognized datatype-clash

> When talking about datatypes we are 
> forced into talking about information 'inside' RDF and information 
> coming from 'outside'. The 'side' that these words are referring to 
> is  the boundary of a hypothetical RDF reasoning engine.
> I note that the XML spec makes a similar reference to a hypothetical 
> XML parser, and it does not seem inappropriate there.

(a) I think it is very inappropriate there; I fought
tooth-and-nail to keep it out, but lost. I think
the cost has been much higher than the benefit.
(b) the XML WG did not introduce that term lightly.
There were endless discussions of what constraints
to put on XML processors. Endless in the sense
that they continue to this day...

> Pat
> -- 
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Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 10 December 2002 12:23:00 UTC

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