W3C home > Mailing lists > Public > www-rdf-logic@w3.org > June 2002

RE: properties as nodes etc.

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 27 Jun 2002 14:43:35 -0500
Message-Id: <p05111b20b94118abda49@[65.217.30.113]>
To: "Danny Ayers" <danny666@virgilio.it>
Cc: www-rdf-logic@w3.org

>  >WHY is this perceived as a problem? What use is there in referring
>>to edges?
>
>hmm...
>
>[the cat] --[sat on]--> [the mat]
>                 |
>               [for]
>                 |
>                 V
>             [an hour]

Ah, I see where you are coming from. OK, but look, there are several 
different things here. There is the property of sitting on something, 
in general; there is a particular instance of that property, which in 
this case might be something like the cat's way of sitting on the mat 
(that's the 'trope'); and then there is a particular occurrence of a 
sitting: an event, or happening, or maybe a 'situation' in Barwise's 
sense, or what Hobbs calls an 'eventuality'.  Its the latter that 
have times and places and which cause other things to happen. I would 
suggest that if you want to talk about things like that, then you 
ought to do so explicitly. One tried-and-tested idea is to introduce 
an explicit category of events, and connect everything else to them. 
Then your example would look like this in Ntriples:

_:x  rdf:type sittingsOn .
_:x  agent cat .
_:x  object mat .
_:x  duration hour .

where you would also know that

sittingsOn rdfs:subClassOf events .

and you could then say other things about that sitting as well, such 
as why it happened and what its results were and who told you about 
it, and so on. You could even say that it never happened or was 
imaginary.

>could currently be broken down something like :
>
>[sat on] --[subclass]--> [sat on for an hour] 
>
>[the cat] --[sat on for an hour]--> [the mat]
>
>[sat on for an hour] --[cardinality]--> [1]
>
>but it seems less clunky to say :
>
>[sat on for an hour] --[instanceOf]--> [sat on]
>
>[the cat] --[sat on for an hour]--> [the mat]

Sure, that's a quick way to do it if you aren't too concerned about 
extending it with other properties.

>
>but then is [sat on] in the first figure really an arc?

No, its a node. But like I said, that's fine: you can use the same 
uriref as a node and as an arc.

Pat

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Received on Thursday, 27 June 2002 15:43:33 GMT

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