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a review of 'RDF Datatyping'

From: Dan Connolly <connolly@w3.org>
Date: 23 Aug 2002 09:00:18 -0500
To: w3c-rdfcore-wg@w3.org
Message-Id: <1030111219.13314.28.camel@dirk>

Some review comments on

  Last Modified: 19 August 2002

Hmm... 'datatyping'? it's a verb?
I'd rather something like

	Using Primitive Datatyps in RDF

The editors are listed as:

  Pat Hayes,
  Sergey Melnik,
  Patrick Stickler,

Have they all looked at it? Maybe there
should be an asterisk or something by
the folks that haven't read it yet.

The introductory text (abstract, status,
introduction, desiderata) look like
they haven't gotten much attention for
a while, so I'm not reviewing them
closely. The verbification of datatype
shows up in "1.1 What is Datatyping?"
again, though.

| RDF literals are structured objects consisting of
| a string, which is optionally qualified as
| XML content (rdf:parseType equal to "Literal")
| and/or having an associated xml:lang value

I think this view of literals is confusing people;
as I have said in discussion of the model theory,
I think it's less confusing to explain it so
that literals are a union of
	XML infoitem
	XML info-item-with lang

| The conceptual framework for RDF datatyping
| presented in this specification is compatable
| with the type system defined by XML Schema
| for both simple and complex datatypes.

Complex datatypes??? We don't even handle
facets on the primitive types, let alone
complex types. Hmm... but this doesn't
look like a typo; there's further discussion
of the concept and even an example. I'm
not interested in this aspect of the design.
I'd rather it were left out.

| For an XML Schema complex datatype, its value
| space is the set of all valid infosets licensed
| by its content model and its datatype mapping
| is the mapping from each XML serialization to
| its corresponding infoset. 

Really? Which part of the XML Schema spec
does that come from? Please cite it by

| 3.2 Global Datatyping

verbification again.

| Global datatyping leaves the datatype of the
| property value implicit

which property? Ill-formed definite descriptions
are a major pet-pieve of mine.

The use of rdf:type with values of datatypes
seems to complicate life considerably...

You seem to be using the entailment...

  ex:age rdfs:range xsd:integer .
  Jane ex:age "25" .
  "25" rdf:type xsd:integer

which makes a certain amount of sense (though
I don't think it follows from current model
theory drafts, because of the literal in the
subject position), but note that "25" might get
related to any number of classes by the
rdf:type property this way. Does the model
theory in this spec handle all those cases?

Hmm... the model theory seems to use
rdfs:range directly, rather than using
the rdf:type conclusion that follows
from rdfs:range... so it won't work
with stuff like DAML+OIL restrictions.

I see section 6.1.3 DAML+OIL doesn't
have much stuff in it.

Consider something like

	:Person rdfs:label "Person";
		rdfs:subClassOf [
		  ont:onProperty :age;
		  ont:toClass xsdt:integer;

I gather the DAML+OIL crowd expects to
be able to do stuff like that. And it won't
work with this model theory, because the
DAML restriction stuff goes right past
rdfs:range to rdf:type.

Well... that's all for now. Time for the telcon.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 23 August 2002 10:00:19 UTC

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