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Re: Sloppy inference rules

From: Ivan Herman <ivan@w3.org>
Date: Wed, 7 Nov 2012 08:29:50 -0500
Cc: Pat Hayes <phayes@ihmc.us>, Guus Schreiber <guus.schreiber@vu.nl>, RDF WG <public-rdf-wg@w3.org>
Message-Id: <1D54ACF9-1983-485B-B622-4019D60652B9@w3.org>
To: Richard Cyganiak <richard@cyganiak.de>

On Nov 7, 2012, at 06:20 , Richard Cyganiak wrote:

> On 30 Oct 2012, at 16:15, Pat Hayes wrote:
>> So my question to the WG is, how disastrous would it be if the RDFS inference rules were stated in terms of a 'sloppy' version of RDF with the syntactic restrictions removed, i.e. with the following grammar for triples?
>> 
>> triple ::= term term term .
>> term ::=  IRI | blanknode | literal
> 
> +1

Let us remind ourselves, by the way, that (per agreement at the F2F) the RDF(S) inference rules are the subject of a separate, non-normative Working Group Note; the normative semantics continues to be the model theoretic one. Ie, if, for the purpose of the notes, such generalized triples are used, that does not affect RDF normatively.

Having such 'generalized' triples in for the purpose of the inference rules is therefore perfectly o.k., but I would also like to see two things added to the note:

- drawing attention on the fact that these triples go beyond RDF triples, and they are there for the purpose of getting the rules working
- making it clear that the rule engine is supposed to throw away non-RDF triples at the end of processing when returning an expanded graph.

I also realize that doing this means that, formally, we can forget about those confusing rules that 'replace' literals with blank nodes. Which is fine for the rule set but it may be worth keeping a note in the text making clear to implementers that, if they rely on RDF comformant environments, that is a possible approach they may use (actually, as of today, I would probably not even use blank nodes there, because that is always a scary thing to refer to, but rather skolem URI-s, now that we have them...)

Ivan

> 
> Best,
> Richard


----
Ivan Herman, W3C Semantic Web Activity Lead
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Received on Wednesday, 7 November 2012 13:30:25 GMT

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