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Re: What is a property?

From: Krzysztof Janowicz <janowicz@ucsb.edu>
Date: Fri, 5 May 2017 10:26:14 -0700
To: Maxime Lefrançois <maxime.lefrancois@emse.fr>, Raúl García Castro <rgarcia@fi.upm.es>, SDW WG Public List <public-sdw-wg@w3.org>, "Cox, Simon (CESRE, Kensington)" <Simon.Cox@csiro.au>, Armin Haller <armin.haller@anu.edu.au>
Message-ID: <b6c84bfb-75d5-9dc0-b650-04010648083d@ucsb.edu>
Hi,

See also Simon's message "In fact in ISO 19109 revision I made sure that 
we left the door open for properties to /not/ be even tied to just one 
feature-type, so that the notion of 'colour' or 'mass' could be denoted 
with the same token regardless of which feature-type it is associated 
with. i.e. no global domain contraints ..."

> @Krzysztof, what do you mean by axiomatic perspective ?

That from the point of view of the axioms both ways would be acceptable.

> Are you sure the intended one is really the second example ? Intended 
> by who ?
>

I mean the example where there is one such thing as 'temperature' (which 
is an ObservableProperty). Whenever you observe, you may involve 
different sensors and carry out your observation on different features. 
While this will create a 'new' observation every time, the 
ObservableProperty will always stay the same. This is also comparable to 
the notion of a procedure. To the very best of my knowledge, this is how 
all the measurement type code lists that I am aware of work, e.g., 
http://vocab.nerc.ac.uk/collection/A04/current/AverageWindSpeed/.

Best,
Krzysztof

On 05/05/2017 09:21 AM, Maxime Lefrançois wrote:
> Hi Krzysztof, Raúl, all,
>
> I will also point to the resources:
> - 
> https://www.w3.org/2015/spatial/wiki/Link_between_FeatureOfInterest_and_xxxProperty#What_is_an_instances_of_ssn:Property_.3F 
>
> - https://lists.w3.org/Archives/Public/public-sdw-wg/2017Apr/0336.html
>
> @Krzysztof, what do you mean by axiomatic perspective ? Are you sure 
> the intended one is really the second example ? Intended by who ?
>
> It really looks to me like only (1) conforms to the original SSN spec.
>
> What I love from (1) is that we can indeed, as Krzysztof mentions, 
> express *both* the Property <OccupancyBuildingX>, and the Property 
> *Type* ex:Occupancy:
>
> ex:Occupancy rdfs:subClassOf sosa:ObservableProperty.
> <OccupancyBuildingX> a ex:Occupancy  ;
>  ssn:isPropertyOf ns:BuildingX .
> <OccupancyBuildingY> a ex:Occupancy  ;
>  ssn:isPropertyOf ns:BuildingY .
>
> This solution has all the advantages of solutions (1) and (2), while 
> being perfectly aligned with the original SSN spec, and cover the 
> competency questions that Raúl and Armin were mentioning.
>
> In addition, Krzysztof brings up one more competency question that (1) 
> covers, while (2) does not:
> - It is possible to extend SOSA/SSN with some vocabulary to describe 
> for instance that: "temperature of body1 is less than of body2". With 
> (2), there is no such concept as "temperature of body 1".
>
>
> So my final suggestion would be to make it clear in the spec and the 
> examples that we adopt (1). I believe it's little effort to adapt 
> existing datasets that were using (2) to the (better/original/new) 
> approach (1)
>
>
> Examples will be highly impacted by the final decision to this 
> question, I will hence delay ACTION-350 until then.
>
> Best,
> Maxime Lefrançois
>
> Le ven. 5 mai 2017 à 17:20, Krzysztof Janowicz <janowicz@ucsb.edu 
> <mailto:janowicz@ucsb.edu>> a écrit :
>
>     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 <mailto:jano@geog.ucsb.edu>
>     Webpage: http://geog.ucsb.edu/~jano/ <http://geog.ucsb.edu/%7Ejano/>
>     Semantic Web Journal: http://www.semantic-web-journal.net
>
>


-- 
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 17:26:51 UTC

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