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Re: help with dated entailments ... (for POWDER)

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 11 Jan 2008 11:03:04 -0800
Message-Id: <p0623090bc3ad6c7821fe@[]>
To: Jeremy Carroll <jjc@hpl.hp.com>
Cc: Owl Dev <public-owl-dev@w3.org>

At 11:03 AM +0000 1/11/08, Jeremy Carroll wrote:
>(originally sent to OWL WG; where Bijan replied, and I will follow 
>up to his message here)
>In my analysis of what is going in POWDER I have now written
>I have a question.
>POWDER includes two properties wdr:validFrom and wdr:validUntil.
>Inbetween these dates then an example like:
>should 'entail'
>Outside these dates the 'entailment' is not known to hold.
>Clearly a full formal treatment of time is well outside the scope of
>what will be included in the POWDER specification.

Well, maybe not. You don't have to deal with branching futures and 
all that other crap. Just say that time is a totally ordered set of 
dateTimes, specifying the resolution you want, and say that 
ontologies make assertions at times (and not at others), so that your 
example is effectively the empty ontology (asserts nothing) before 
its validFrom and after its validTo. This isn't strictly an RDF 
*extension*, but its damn close.


>So how do I hack it?
>Or perhaps more positively, how do I express pragmatically the
>I have to define a semantic extension to RDF, so I have quite a lot of
>wiggle room, but need to use it cautiously.
>I'll try writing a straw man and adding it to the page.
>Might take an hour or two.
>Note for the DL people - I need to also articulate how my approach
>relates to OWL DL.

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Received on Friday, 11 January 2008 19:03:16 UTC

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