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Re: What is a property?

From: Maxime Lefrançois <maxime.lefrancois@emse.fr>
Date: Mon, 08 May 2017 12:03:17 +0000
Message-ID: <CALsPASUEnXE-SyehyMN6N5N-yqk88EE=CGvxneP+y4SrmvuZSg@mail.gmail.com>
To: Simon.Cox@csiro.au, janowicz@ucsb.edu, rgarcia@fi.upm.es, public-sdw-wg@w3.org, armin.haller@anu.edu.au
Hi Simon, all,


Let me propose a translation of the ISO 19109 model to RDF:

(1) there are Feature-types (classes), and Features of interest (instances
of those classes)
--> Feature-types are RDFS/OWL Classes, they are sub-classes of
sosa:FeatureOfInterest, and their instances are Features of Interest

ex1: ex:Room is a RDFS/OWL class that represents a Feature-type, and
<roomX> is an instance of that class that represents a Feature (of Interest)
ex2: ex:Building is a RDFS/OWL class that represents a Feature-type, and
<buildingX> is an instance of that class that represents a Feature (of
Interest)

(2) there are properties, and these properties may have instances.
--> properties are RDFS/OWL Classes, sub-classes of sosa:ObservableProperty
(and by transitivity, also of ssn:Property), and their instances are named
"property instances".

ex: ex:Occupancy is a RDFS/OWL class that represents a Property.
<buildingXoccupancy> and <roomXoccupancy> are instances of that class and
represent "property instances".


Then:

(a) a property instance cannot exist in the absence of a feature (of
interest)

ex1:  <buildingXoccupancy> cannot exist in the absence of <buildingX>
ex2: <roomXoccupancy> cannot exist in the absence of <roomX>

(b) Feature-types (classes) are characterized by a set of properties

ex1:  ex:Building is characterized by a set of properties, and this set
contains property ex:Occupancy

ex:Building rdfs:subClassOf [
  owl:onProperty ssn:hasProperty ;
  owl:someValuesFrom ex:Occupancy ] .

<buildingX> rdf:type ex:Building   ;
  ssn:hasProperty <buildingXoccupancy> .

<buildingXoccupancy> rdf:type ex:Occupancy .


(c) But each (well most, anyway) property may relate to more than one
feature-type (and implicitly to many more than one individual feature)
--> ex:Occupancy can relate to more than ex:Building, it can also relate to
ex:Room.

ex:Room rdfs:subClassOf [
  owl:onProperty ssn:hasProperty ;
  owl:someValuesFrom ex:Occupancy ] .

<roomX> rdf:type ex:Room ;
  ssn:hasProperty <roomXoccupancy> .

<roomXoccupancy>  rdf:type ex:Occupancy .



To me, everything is fine there:
 - what is named "xxx-type" is translated in RDFS/OWL as a class
 - what is named "xxx instance" is translated in RDFS/OWL as an instance

ex1: for Feature-type and feature (of interest)
- Feature-types are translated in RDFS/OWL as classes
- Features (of interest) are translated in RDFS/OWL as instances.

ex1: for properties and their instances:
- observable (and actuatable) properties are made classes
- instances of theses properties are instances.



If instead we want to translate ISO 19101 properties into rdf:Properties
(or owl:ObjectProperties), then [1] and [2] propose some way to do it, that
is totally compatible with the above description. The suggestion would be
to translate ISO 19101 properties into both:
  1. a sub-class of sosa:ObservableProperty, and
  2. a (functional) sub-property of ssn:hasProperty


ex:occupancy a owl:ObjectProperty , owl:FunctionalProperty ;
  rdfs:subPropertyOf ssn:hasProperty ;
  rdfs:range ex:OccupancyProperty .

ex:OccupancyProperty a rdfs:Class ;
  rdfs:subClassOf sosa:ObservableProperty .

 ex:Building rdfs:subClassOf [
  owl:onProperty ex:occupancy   ;
  owl:someValuesFrom ex:OccupancyProperty ] .

ex:Room rdfs:subClassOf [
  owl:onProperty ex:occupancy ;
  owl:someValuesFrom ex:OccupancyProperty ] .


<buildingX> rdf:type ex:Building   ;
  ex:occupancy <buildingXoccupancy> .

<buildingXoccupancy> rdf:type ex:Occupancy .

<roomX> rdf:type ex:Room ;
  ex:occupancy <roomXoccupancy> .

<roomXoccupancy>  rdf:type ex:Occupancy .


Any comments?

Best,
Maxime

[1] - https://lists.w3.org/Archives/Public/public-sdw-wg/2017Feb/0478.html
[2] - https://lists.w3.org/Archives/Public/public-sdw-wg/2017Feb/0515.html

Le lun. 8 mai 2017 à 02:49, <Simon.Cox@csiro.au> a écrit :

> ISO 19109 model in its revised form says
>
> (a)   A property instance cannot exist in the absence of a feature (of
> interest)
>
> (b)   Feature-types (classes) are characterized by a set of properties
>
> (c)    But each (well most, anyway) property may relate to more than one
> feature-type (and implicitly to many more than one individual feature)
>
> This was intended to respect both the ISO 19101 reference model, and the
> semantic web toolkit.
>
>
>
> When working in the RDFS/OWL world we could just make these observable
> (and actuatable) properties RDF properties. i.e.
>
>
>
> ssn:Property owl:equivalentProperty rdf:Property .
>
>
>
> is OK to me, but because of the way that rdf:Property is built-in to RDF
> itself, I’m not sure if the meta-model allows us to go on to say
>
>
>
> sosa:ObservableProperty rdfs:subClassOf ssn:Property .
>
>
>
> and then
>
>
>
> sosa:Observation
>
>   rdfs:subClassOf [
>
>       rdf:type owl:Restriction ;
>
>       owl:allValuesFrom sosa:ObservableProperty ;
>
>       owl:onProperty sosa:observedProperty ;
>
>     ] .
>
>
>
> (or sosa:observedProperty rdfs:range sosa:ObservableProperty . )
>
>
>
> Simon
>
>
>
> *From:* Krzysztof Janowicz [mailto:janowicz@ucsb.edu]
> *Sent:* Saturday, 6 May, 2017 03:26
> *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
> (L&W, Clayton) <Simon.Cox@csiro.au>; Armin Haller <armin.haller@anu.edu.au
> >
> *Subject:* Re: What is a property?
>
>
>
> 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> 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
> Webpage: http://geog.ucsb.edu/~jano/
> 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 Monday, 8 May 2017 12:04:33 UTC

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