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Re: semantics of daml:UnambiguousProperty

From: Je'ro^me Euzenat <Jerome.Euzenat@inrialpes.fr>
Date: Fri, 26 Jan 2001 22:03:27 +0100
Message-Id: <a05010400b6970d4037be@[194.199.22.158]>
To: Dan Brickley <danbri@w3.org>, Jonathan Borden <jborden@mediaone.net>
Cc: <www-rdf-logic@w3.org>
Hello list,

In his message (Re: semantics of daml:UnambiguousProperty) of 24/01/01,
Dan Brickley wrote:
>  > Dan Brickley wrote:
>  > >
>  > > A little question re DAML+OIL semantics. If a property is an unambigous
>>  > property, does the equality specified by DAML+OIL below hold only at a
>>  > particular point in time or does it hold across time and change?
>>  >
>  > > Eg. if I say some resource X has a foo:contact property
>  > > whose value is some other resource Y, where Y is "the resource  whose
>>  > personalMailbox is mailto:lighthouse-keeper@stonyisland.example.com", what
>>  > does this mean? Might Y differ over time, so long as at any one time there
>>  > was only a single resource with that property/value pair. What inferences
>>  > does daml:UnambiguousProperty license in this respect?
>  > >
>>  Doesn't this depend entirely on the model? Either this mailBox is or isn't
>>  unambiguously associated with a single person err resource. If arcs are
>>  present between two URIs representing two people and this URI then this URI
>>  is not a good value for this resource. Alternatively when such a value is
>>  defined, perhaps it should flag an error to enter a second arc.
>
>Problem is that there are two realworld scenarios that we might want to
>distinguish. One is where the semantics of some predicate allow, at any
>one time, at most one value for that property on any given resource. At
>different times, different resources may take that role. The
>other scenerio is where we know that role will only ever have a single
>occupant. It was a slightly mischievous question in that neither RDF nor
>DAML+OIL make any explicit acknowledgement of time, change and other such
>nuisances. TimBL suggested I ought to be using daml:UnambiguousProperty
>for an app I'm working on, so I need to find out whether this property
>has the stronger sense. Hopefully this can be clarified without getting
>into the business of defining theories of time and the like.

It seems to me that DAML+OIL (and all such languages) does not 
consider time. The operators are defined with regard to a set of 
assertions. So the correct interpretation should then be:

"(at any one time) at most one value for that property on any given resource"

Your particular problem seems to be relevant to Upate and revision. A 
topic that has been studied for some time now. It does not necessary 
require a specific theory of time (the good news), but often very 
complex (in the comptational complexity sense) logical apparatus (the 
bad news).

But there is another issue raised by your initial message:
>  > > Eg. if I say some resource X has a foo:contact property
>  > > whose value is some other resource Y, where Y is "the resource  whose
>  > > personalMailbox is 
>mailto:lighthouse-keeper@stonyisland.example.com", what
>>  > does this mean? Might Y differ over time, so long as at any one time there
>>  > was only a single resource with that property/value pair. What inferences
>  > > does daml:UnambiguousProperty license in this respect?

It does not seems to me that you can interpret anything as "the resource  whose
personalMailbox is mailto:lighthouse-keeper@stonyisland.example.com" 
(as far as there is no description of personalMailbox to be a 
definitional attribute for the class of Resources, or say People for 
being more specific).
It seems quite possible that there are several People sharing the 
same mailbox and it is just one of them that is the contact.

Moreover, it seems to me that you are considering here that the 
unambigousProperty is contact but that the non-ambiguity is 
propagated (maybe in virtue of the anonymity of the intermediate 
Resource) to personalMailbox. I might misinterpret your thinking, but 
if I am right, this should not be interpreted that way.



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Received on Friday, 26 January 2001 16:04:28 GMT

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