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Re: (tentative) container model proposal

From: Dan Brickley <danbri@w3.org>
Date: Thu, 7 Jun 2001 18:32:59 -0400 (EDT)
To: Dan Connolly <connolly@w3.org>
cc: <w3c-rdfcore-wg@w3.org>
Message-ID: <Pine.LNX.4.30.0106071805120.29416-100000@tux.w3.org>
On Wed, 6 Jun 2001, Dan Connolly wrote:

> Dan Brickley wrote:
> >         http://www.w3.org/2001/05/rdf-c/ (copied below in text form)
> [...]
> > I am well aware that the proposal is currently in a skeletal state, and
> > lacks test cases. I hope it provides at least some useful background for
> > discussion on friday. Regarding test cases, I have to say I'm stumped: the
> > implementations this relate to are databases, APIs etc rather than
> > parsers, and I am not sure how best to represent tests of that kind.
> Er... maybe I'm missing something, but I read it twice, and it
> seems to reduce to this simple test case: is this an RDF
> document or not?

I have heard it suggested (on www-rdf-interest and personal communication)
that, whilst this sort of file is an RDF document, the language of
paragraphs P189 thru P193 of M+S (see
imposes behavioural constraints on RDF databases, query engines etc. For
example, I think there was some discussion regarding the Mozilla RDF
API's "proper" behaviour if a element is removed from a list via the API.

Some people have appeared to say "yes this is an RDF doc" to your test,
yet believe P189-P193 impose behavioural requirements on RDF

> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
>     <rdf:Description>
>         <rdf:_1>abc</rdf:_1>
>         <rdf:_3>def</rdf:_3>
>     </rdf:Description>
> </rdf:RDF>
> The simplest answer that meets my needs is: yes, that's
> an RDF document. The parts of the spec that suggest
> otherwise are an error.

I agree. Would you support the removal of P189-193 from the "RDF formal
model" section of the spec?

> To my mind, anything that suggest that containers are
> fundamental in any way -- that they are anything
> more than a standardized vocabulary of classes and
> properties and some syntactic sugar -- is an error.


> Now this doesn't resolve either of the active issues you
> own, danbri, so maybe I missed the gist of your proposal.
> http://www.w3.org/2000/03/rdf-tracking/#rdf-containers-syntax-ambiguity
> http://www.w3.org/2000/03/rdf-tracking/#rdf-containers-syntax-vs-schema

[ * danbri does some ACTION archaelogy ]

This appears to have mutated slightly since I was originally ACTION'd in
the first meeting; my apologies for not clarifying things sooner.


	Issue Discussion
	We discussed 3 technical issues:

	The XML Namespace spec doesn't address unprefixed attributes. We'll have
	to live with their bug. RESOLVED: We'll strongly recommend the use of
	namespace qualified attributes, and allow but deprecate unqualified
	Ora noted that it was an original requirement for RDF that parsing should
	not require knowledge of the schema.
	The discussion on the latter 2 issues largely occurred in parallel and
	became a more general discussion about containers. Several people
	advocated deprecating container types and/or making them a separate module
	(this also applies to reification).

	It also brought out several larger issues:

	RDF Syntax vs. Model
	We should record more of the history behind various RDF issues.
	What is the real-world use of containers and other RDF features? What will
	break if we change stuff? ACTION (everyone): send RDF feature usage
	information from real-world applications you know of to Guha, who will
	collect it.
	Modularization can be accomplished via namespaces or documents.
	Redefinition of the RDF(S) namespaces may not be required.
	ACTION: Dan Brickley will own the "container problem". Ora Lassila will

My action (followed up after the call in a jetlagged discussion with
Ora in Hong Kong) was a follow on from the minuted observation that "The
discussion on the latter 2 issues largely occurred in parallel and became
a more general discussion about containers". The "container problem" that
I went away with Ora to summarise was to look at some of the
broader-than-syntax problems with containers that we touched on in that
call, and come back with an account of the model-oriented (rather than
pure syntax) problems. We focussed on the privileged role given to
containers in the model.

Having convinced myself there is indeed an issue here, I believe it
deserves a separate place in the issue list.

Proposed issue summary:

Parags 189-193 of M+S suggest a privileged role for RDF containers within
the formal model at the heart of RDF. Furthermore, they suggest
largely unimplemented (**need to hear about Jan's
implementation**) constraints, either on XML encodings of RDF, on other
(eg. database implementations) or on both. These paragraphs are either in
error (RDF does allow for partial descriptions) or editorially redundant:
in either case they should be removed.

Received on Thursday, 7 June 2001 18:33:06 UTC

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