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Re: is rdf a regular logic? RIF? was: Coherent Logic (a.k.a Geometric Logic) and RDF?

From: Patrick J Hayes <phayes@ihmc.us>
Date: Wed, 22 Jan 2020 16:29:54 -0600
CC: Jos De Roo <jos.deroo@agfa.com>, semantic-web <semantic-web@w3.org>
Message-ID: <A5261578-744B-40D2-A2F7-3A5A1CAF8AD0@ihmc.us>
To: Henry Story <henry.story@bblfish.net>


> On Jan 22, 2020, at 8:22 AM, Henry Story <henry.story@bblfish.net> wrote:
> 
> 
> 
>> On 19 Jan 2020, at 06:06, Patrick J Hayes <phayes@ihmc.us> wrote:
>> …
>>> 
>>> PS. I think I remember Pat Hayes claiming RDF was a first order logic
>>> on this list a year or so ago… (that would I presume not fit it being
>>> a regular logic,… But I am not an expert in this (yet).
>> 
>> RDF is a (very minimal) fragment of FOL. Technically it is binary (relations of arity 1 or 2) FOL restricted to conjunction and the existential quantifier. No negation, disjunction or universal quantifier. It also lacks any scoping mechanism, but this does not matter when there is no negation, disjunction or universal quantification. One would get full FOL by adding negation and a scoping mechanism (such as an explicit existential quantifier, although other syntaxes could be used.)
> 
> yes, so that is why it looks so close to regular logic as far as I understand.

Looks like it, indeed. I was not familiar with this ‘regular’ terminology. It is also closely similar to CSPierce’s “existential graphs” from around 1880 (though Pierce also had scoping and negation, so RDF is, again, a sublanguage of Pierce’s notation.) I find it interesting that this particular weak but useful, and eminently ’graphable’, logic has been reinvented so many times since the very beginning of modern logical studies. 

Pat

> 
Received on Wednesday, 22 January 2020 22:30:04 UTC

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