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Re: working on it

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Thu, 26 Jun 2003 12:00:41 +0100
Message-ID: <3EFAD259.7090509@hplb.hpl.hp.com>
To: w3c-rdfcore-wg@w3.org


(escaped early)

Pat

we still have to *decide* whether we want to go the way in the documents you
produced last week, or along the lines of the after hours conversation.

Personally, on relfection, and on consulation with my colleagues, I prefer
  the earlier version with iff conditions.

http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Jun/0160
[[
It seems like rather a big change to make at this late stage. Would you be
confident there weren't other properties that need to be declared by fiat
that haven't yet been identified?
]]
[[
These rules may be a nuisance but they are not a major obstacle.
They don't look difficult or expensive to implement.

Given that the result of the rewrite would be, in some sense,
less clean I would think it would need some additional motivation than just
moving a couple of obscure rules slightly further down in the appendix.
]]

Further, every entailment rule with an rdfs:subPropertyOf or rdfs:subClassOf
on the RHS is using the extensionality of these properties. i.e. six of the
thriteen rdfs rules in the last call version. I think that that suggests that
the extensionality is an important aspect of these properties even from a
rule perspective.

Dan argued that given a bug is it obvious whether we fix it by fixing the
entailment rules or fixing the model theory - he argued that it was not.

Continuing on the programming metaphor, given a bug, it is usual to try and
preserve the contract with the user, and to only change that contract when
the bug shows that it was a bad contract. The contract we have agreed is a
model theoretic contract; the extensionality contract is easier to understand
than one with the special aspects of subClassOf and subPropertyOf declared by
fiat; horst-01 does not indicate in the slightest a bug with the contract,
merely a bug with the implementation. In such a case the contract should be
preserved and the implementation fixed.

Admittedly if these rules were difficult to implement we might want to think
again - but they are not, they are just surprising.

===

Editorial note: it might be clearer to expand the 12 rules to the five
instantions, and drop the ppp and qqq e.g.

12a

rdf:type rdfs:subPropertyOf zzz .
  zzz rdfs:domain yyy .
=>
rdfs:Resource rdfs:subClassOf yyy .

12b
rdfs:subClassOf rdfs:subPropertyOf zzz .
  zzz rdfs:domain yyy .

rdfs:Class rdfs:subClassOf yyy .


....

Jeremy

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Received on Thursday, 26 June 2003 07:01:34 EDT

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