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Re: What is a property?

From: Krzysztof Janowicz <janowicz@ucsb.edu>
Date: Fri, 5 May 2017 08:20:59 -0700
To: Raúl García Castro <rgarcia@fi.upm.es>, SDW WG Public List <public-sdw-wg@w3.org>
Message-ID: <fba1be05-5fbe-3e44-ea57-d216ea315777@ucsb.edu>
Hi,

Both uses are okay from an axiomatic perspective, but the indented one 
is the second example. It is worth noting that they are not as different 
as they may seem because (1) can be made very similar to (2) by adding a 
subclassing axiom that states

Occupancy rdfs:subClassOf ObservableProperty.

and then change

ns:OccupancyBuildingX a ssn:Property ; [KJ: should be ObservableProperty]
...

to

ns:OccupancyBuildingX a Occupancy.

The question is rather how specific we should be to foster 
interoperability between different datasets, and, IMHO, we should 
clearly state what we mean. There is a 1:2 relation between observable 
properties and features  (and observations). Science works because no 
matter how often we measure the temperature of a body and how many 
different sensors and bodies we use, the measured property is of the 
same kind, namely temperature. This, for instance, makes sure that we 
can state that the temperature of body1 is less than of body2 and so on.

Best,
Jano


On 05/05/2017 07:50 AM, Raúl García Castro wrote:
> Dear all,
>
> Taking a look to a previous thread 
> (https://lists.w3.org/Archives/Public/public-sdw-wg/2017Apr/0335.html) 
> and to a recent pull request conversation 
> (https://github.com/w3c/sdw/pull/792) it seems that there are two 
> views on what a property is.
(1)
> Is it something intrinsic to a feature?
>   ns:OccupancyBuildingX a ssn:Property ; [KJ: should be 
> ObservableProperty]
>     ssn:isPropertyOf ns:BuildingX .
>   ns:OccupancyBuildingY a ssn:Property ; [KJ: should be 
> ObservableProperty]
>     ssn:isPropertyOf ns:BuildingY .

(2)
>  Or is it something independent of a concrete feature?
>   ns:Occupancy a ssn:Property ; [KJ: should be ObservableProperty]
>     ssn:isPropertyOf ns:BuildingX .
>     ssn:isPropertyOf ns:BuildingY .
>
> For those familiar with QUDT, is a Property related to a qudt:Quantity 
> (first option above) or to a qudt:QuantityKind (second option)?
>
> Note that both options are supported by current definitions and usage 
> information, so we need to define clearly what we understand as a 
> Property and update the definitions and examples to leave it clear.
>
> Kind regards,
>


-- 
Krzysztof Janowicz

Geography Department, University of California, Santa Barbara
4830 Ellison Hall, Santa Barbara, CA 93106-4060

Email: jano@geog.ucsb.edu
Webpage: http://geog.ucsb.edu/~jano/
Semantic Web Journal: http://www.semantic-web-journal.net
Received on Friday, 5 May 2017 15:21:36 UTC

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