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Re: Concerns about reification

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Tue, 19 Feb 2002 17:35:56 +0000
Message-Id: <>
To: Sergey Melnik <melnik@db.stanford.edu>, RDFCore WG <w3c-rdfcore-wg@w3.org>
Cc: Frank Manola <fmanola@mitre.org>
Hi Sergey,

At 10:11 15/02/2002 -0800, Sergey Melnik wrote:
>Brian asked me (for the Xth time, sigh) to express my concerns about
>reification in writing. My position remains that we need an
>interoperable and efficient way of doing reification.

I'm sorry about the repeats.

>If we go for "stating" (answer "No" to Q1 in [1]), no special semantics
>is associated with the vocabulary rdf:Statement, rdf:subject,
>rdf:predicate and rdf:object. This means applications *cannot
>interoperate* using this vocabulary since its meaning is unspecified.
>Effectively, going for "stating" amounts to deprecating 4-triple
>reification as used today.

I see what you mean here, and I agree with it, though I think you express 
it a bit too forcefully.  There was no model theory in M&S at all, but 
folks seem to have managed to do useful things with it.  Thus, even without 
model theoretic semantics, the reification vocabulary can be used, and 
provided you understand the semantics attached to it by a particular 
application, then you can do useful things with it.

But I agree with you, that it defines no semantics that apply across the 
board to all applications.

>If we go for "statement" (answer "Yes" to Q1 in [1]), we get a (rather
>painful, admittedly, but endorsed) way of referring to statements found
>on Web pages and in RDF databases, recording provenance etc. This is IMO
>much more concrete and useful that just providing no definition at all,
>although the usability of 4-triple reification still remains seriosly
>hampered by its verbosity.
>In summary, if we go for "stating" we have *no* official mechanism for
>reification. In this case we'd have to suggest an alternative, we cannot
>just wash our hands. It is an illusion that we can leave the vocabulary
>undefined and at the same time recommend developers to use it in a
>consistent way. If we go for "statement" we do have a solution, albeit a
>poor one. If we run out of time in finding an alternative *efficient*
>way of doing reification, we could of course fall back on "statement"
>expressed using 4 triples. In this case, we would not have achieved much
>since inefficiency proved to be a show stopper for using 4-triple
>reification in the past 3 years.

We have run out of time.  However, there has been talk on this list of some 
folks getting together and proposing new vocabulary, possibly publishing as 
a note.  That could be a way forward.

There has been strong support in the WG for the position we have now 
reached.  I have not officially closed the issue, though I plan to put it 
up for closure this week, if Frank agrees that is appropriate.

Received on Tuesday, 19 February 2002 12:37:43 UTC

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