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Re: (Round 2) Proposed Extensions to OWL

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Fri, 27 Jun 2003 20:26:43 +0100
Message-ID: <3EFC9A73.90107@hplb.hpl.hp.com>
To: "Thomas B. Passin" <tpassin@comcast.net>
CC: www-rdf-interest@w3.org


I think I like this treatment.

Jeremy

Thomas B. Passin wrote:

> [Roger L. Costello]
> 
>>2. There is a relationship between
>>
>>        concat(rdf:value, units) in resource #1, and
>>        concat(rdf:value, units) in resource #2.
>>
>>    "There is a relationship between the concatenation of the
>>     value of the rdf:value property with the value of the units
>>     property in resource #1, and a similar concatenation of
>>     values in resource #2."
>>
>>    The relationship is:
>>
>>       1.0 inch = 2.54 centimeter
>>
>>Do you agree that this is the relationship between the two
>>anonymous resources?
>>
> 
> No, I do not. Trying to stick close to the way you have set this out, there
> is not a direct relationship between the __concatenations__ of unit and
> value.  You could say there is a relationship between the __tuple_s_  (1.0,
> inch) and (2.54, cm), but that is still superficial because it depends on
> the number of significant figures and the round-off strategy.   I would
> rather have it be more fundamental.
> 
> Here is what we know, it seems to me -
> 
> 1) Both resources are length measures.
> 2) The value of a length measure can be expressed numerically in different
> units.
> 
> (This is a scalar quantity.  A more complex quantity, like a vector or
> tensor, would have to be expressed as some structured value).
> 
> We know a few other things, but they can be formulated in various ways.
> Here is one way.
> 
> 3) The numerical value of a length measure may be obtained by applying an
> operator (or a transformation) to it.  That is, conceptually
> length-in-inches = L1 * M, where L1 is the operator for getting the length
> in inches, and M is the measure.
> 
> 4) A measure may have any number of such operators or transforms, one for
> each different unit of measure.
> 
> Here is a set of triples (minus namespaces) for your two resources that
> captures, I think, the essence of these points -
> 
> {resource
>     {type:length-measure}
>     {value:
>         transform:
>             {
>                 type:length-in-inches}
>                 number: 1
>             }
>     }
> }
> 
> {resource
>     {type:length-measure}
>     {value:
>         transform:
>             {
>                 type:length-in-cm}
>                 number: 2.54
>             }
>     }
> }
> 
> I think that these are admirably simple, and I doubt that you can simplify
> them any more without losing their essence.
> 
> The resource type can obviously be stated in OWL as part of an ontology, and
> so can the transform type.  If we had a standard way to make math statements
> with OWL, we could make an OWL statement that the two transforms (inch and
> cm) had some kind of "equivalentValueTo" relationship.
> 
> This approach takes the matter of the relationship between length in cm and
> length in inches away from the individual resources and puts in onto the
> expression of the relationship between the transform types.  I think this is
> very appropriate.
> 
> The upshot is that you need to come up with some convention for expressing
> the relationship between the transforms - or of testing for equivalence -
> and then everything else can be handled in OWL.
> 
> Cheers,
> 
> Tom P
> 
> 
> 
Received on Friday, 27 June 2003 15:27:24 GMT

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