W3C home > Mailing lists > Public > public-sdw-wg@w3.org > December 2016

Re: isObservedBy - was RE: Comments on the SOSA and SSN implementations

From: Krzysztof Janowicz <janowicz@ucsb.edu>
Date: Fri, 16 Dec 2016 09:12:10 -0800
To: public-sdw-wg@w3.org
Message-ID: <29ba17a5-0db5-d2fa-ff07-1f5e3226870c@ucsb.edu>

Unfortunately, I cannot be at the F2F and I am trying to catch up with 
all the many incoming SSN emails :-). Meanwhile you would do me a great 
favor if we would not rush any substantial decisions even if they look 
like minor changes initially. Just think back to our owl:class 
discussion and other cases where we wanted to drop classes, axioms, and 
so forth. It does not make sense to rush these decisions.

Wrt this particular case: sosa:isObservedBy relates an observable 
property to a sensor. It is not the inverse of sosa:madeObservation. We 
will need to work this out in more detail as picking a clear name that 
differentiates between the involved cases will not be trivial. We do not 
have much (formal) semantics in SOSA, so labels will really matter.


On 12/15/2016 02:26 AM, Armin Haller wrote:
> I raised an issue for that: https://www.w3.org/2015/spatial/track/issues/108
> On 15/12/16, 7:55 pm, "Raúl García Castro" <rgarcia@fi.upm.es> wrote:
>      El 15/12/16 a las 3:12, Simon.Cox@csiro.au escribió:
>      >> * sosa:madeObservation
>      > Why is the inverse observedBy property not defined?
>      >
>      > It is present, called 'isObservedBy'.
>      sosa:madeObservation relates a Sensor with an Observation, while
>      sosa:isObservedBy relates an ObservableProperty with a Sensor.
>      That's the reason Krzysztof  was mentioning that we need to think about
>      the naming of these properties.
>      Kind regards,
>      > -----Original Message-----
>      > From: Raúl García Castro [mailto:rgarcia@fi.upm.es]
>      > Sent: Thursday, 15 December, 2016 03:31
>      > To: public-sdw-wg@w3.org
>      > Subject: Comments on the SOSA and SSN implementations
>      >
>      > Dear all,
>      >
>      > I've been reviewing the implementations of SOSA and SSN and here you have some comments (plus a couple of pull requests) on each of them and on the combination.
>      >
>      > SOSA
>      > ----
>      >
>      > * sosa:Platform
>      > The documentation says "(including rdf:type rdfs:Class, owl:Class humans)", should this be "(including humans)"?
>      >
>      > * sosa:Sample
>      >  From the documentation, a Sample is a FeatureOfInterest (shouldn't Sample be a subclass of FeatureOfInterest?). I also think that there is no need for a Sample class; I would just state that a FeatureOfInterest can have as a sample another FeatureOfInterest. In any case, unless some of these changes are made, the current model "does not allow" taking samples of samples.
>      >
>      > * sosa:hasValue
>      > Why not including meta:domainIncludes sosa:Result in this property?
>      >
>      > * Units of measurement
>      > Also, regarding values, I think that right now the ontology falls short on supporting how to describe them when they require a unit of measurement. Along the documentation plenty of examples are included that mention a unit of measurement (e.g., "20m") but in the documentation of sosa:hasValue it only appears "23 or true", without mentioning the unit anymore. Since sosa:hasValue is a datatype property, do we expect people to attach the unit of measurement to a sosa:Result?
>      >
>      > * sosa:hosts
>      > The documentation mentions a SamplingDevice that is not mentioned in the ontology.
>      >
>      > * sosa:madeObservation
>      > Why is the inverse observedBy property not defined?
>      >
>      > * sosa:phenomenonTime and sosa:resultTime I would remove these properties from SOSA, mainly because I think that they aim for a richer level of detail than the other concept descriptions in the ontology.
>      > Having them inside is no main problem, but then their definition is quite weird since one is defined as an object property and the other as a datatype property. I understand why they have been defined that way, but it is not elegant.
>      > On the one hand, in sosa:phenomenonTime we talk about time intervals and instants; we have here an opportunity to link to the W3C Time ontology, and even talk about TemporalEntities?
>      > On the other hand, in sosa:resultTime we talk about xsd:dateTime (being the only property in the ontology that specifies a rdfs:range); to be coherent we should talk about time instants.
>      >
>      > * Importing SKOS
>      > I would move the last triples defining the SOSA ontology to the beginning. Related to these, why do we need to import SKOS?
>      >
>      > SSN
>      > ---
>      >
>      > * ssn:startTime and ssn:endTime
>      > They are not documented in the ontology with rdfs:comment (it happens in others such as observedBy). And the link that appears in the description is "broken" (http://www.w3.org/2005/Incubator/ssn/wiki/SSN_Base#Time).
>      > They are not used in any of the other entities in the ontology; should we remove them?
>      >
>      > * dul:includesEvent
>      > The dul:includesEvent property has dissapeared and the local restriction that relates an Observation to a Stimulus has dissapeared to.
>      > Maybe it has been made in purpose, but the possibility of relating those two classes is not there anymore.
>      >
>      > * ssn:SensorDataSheet
>      > This class is not related to other classes or properties in the model.
>      > Should we remove it or relate it?
>      >
>      > SSN+SOSA
>      > --------
>      >
>      > Taking the SSN ontology as it is (in GitHub) and SOSA, right now it cannot be said that one is a core module of the other, since:
>      >   -  SSN does not reuse SOSA vocabulary terms (this could be implemented by mappings)
>      >   - SOSA adds actuation and sampling
>      >   - SOSA renames plenty of classes and properties. In some cases maybe the intended meaning is more or less equivalent, but in others it radically changes (for example, ssn:hasValue is an object property and sosa:hasValue is a datatype property).
>      >   - The modelling decisions in both are different; for example, in SOSA a Sensor is hosted by a Platform, in SSN a SensingDevice (not a Sensor) is on a Platform.
>      >
>      > The result is that currently we don't have a clean view on the ontology as a whole as a composition of modules. And for anyone using the ontology it will be quite difficult to digest everything (e.g., there are 2 time-related properties in SOSA attached to an observation, in SSN there are another 2 attached to an observation and 2 that are not attached to anything.
>      >
>      > In other words, my opinion is that right now SOSA is something derived from SSN but we still have plenty of work to do (either changing SOSA, SSN, or both) to put them together so it can be considered a proper core module.
>      >
>      > If not, the risk is to produce two different (even if compatible) ontologies which is not desirable for interoperability.
>      >
>      > In other (now more positive) words, I think that SOSA is the result of a very good work, and I'd like it to be a proper core part of SSN.
>      > Let's see how we can do it!
>      >
>      > Kind regards,
>      >
>      --
>      Dr. Raúl García Castro
>      http://www.garcia-castro.com/
>      Ontology Engineering Group
>      Departamento de Inteligencia Artificial
>      Escuela Técnica Superior de Ingenieros Informáticos
>      Universidad Politécnica de Madrid
>      Campus de Montegancedo, s/n - Boadilla del Monte - 28660 Madrid
>      Phone: +34 91 336 65 96 - Fax: +34 91 352 48 19

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, 16 December 2016 17:12:56 UTC

This archive was generated by hypermail 2.4.0 : Thursday, 24 March 2022 20:31:27 UTC