RE: SSN Thread for github issue 378 - Side effects of ssn:Observation being a kind of dul:Event instead of dul:Situation

Weighing in maybe a little late:

One of the motivations for the term ‘result’ in O&M was clarification of the post-condition of the observation, understood as an event.
And (as Josh has pointed out) the concepts of phenomenon-time and result-time were also a part of this story. But O&M also included interpretation, numerical modelling, and forecasting (i.e. when the phenomenon-time is later than the result-time), so we need to be careful here. Perhaps there is a useful taxonomy of observation types on the basis of the relationship between stimuls/phenomenon-time/result-time …

The notion of ‘stimulus’ was a very important contribution from SSN - George Percivall was on my case about this early in the story of SWE, but it didn’t get formalized in the O&M model. But while it is relatively straightforward how it applies to the classical notion of sensing, I need some help to understand what the ‘stimulus’ is for a forecast.

Simon

From: Kerry Taylor [mailto:kerry.taylor@anu.edu.au]
Sent: Monday, 3 October 2016 5:05 PM
To: Joshua Lieberman <jlieberman@tumblingwalls.com>
Cc: Maxime Lefrançois <maxime.lefrancois.86@gmail.com>; SDW WG Public List <public-sdw-wg@w3.org>
Subject: RE: SSN Thread for github issue 378 - Side effects of ssn:Observation being a kind of dul:Event instead of dul:Situation

Hi Josh,
I am not sure I follow – because I am not clear what you mean by “disjoint” here. For me, I meant it as “something cannot be both of those things”,
but perhaps you mean something about non-overlapping time intervals?

If we can’t live with “isPostconditionOf” (and I cannot find any other alternative in dolce myself, but I would be very grateful if someone can) then I can see only 3 other options.

1)       is to disconnect the observation from the stimulus – which seems pretty dumb to me and if so then  I would suggest we go even further and just drop stimulus entirely ( or it could remain connected to a sensor, but if a sensor could respond to multiple stimuli we would have no idea which one provoked this observation.  Which gives another option I suppose – insist that each sensor can have at most one stimulus and then the stimulus could be retrived with the observation by following the sensor – but this is yet another change).

2)       Make up a new term in ssn for the purpose --- but I am not keen to introduce new terms without a really strong reason.

3)      Make up a new term in the alignment (in a new namespace) but not in ssn proper --- I can’t see much value in that for anyone.

I think I can live with “isPostconditionOf”

Maxime, did you spot any other problems with changing observation this way?

--Kerry


From: Joshua Lieberman [mailto:jlieberman@tumblingwalls.com]
Sent: Thursday, 29 September 2016 3:59 AM
To: Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>>
Cc: Maxime Lefrançois <maxime.lefrancois.86@gmail.com<mailto:maxime.lefrancois.86@gmail.com>>; SDW WG Public List <public-sdw-wg@w3.org<mailto:public-sdw-wg@w3.org>>
Subject: Re: SSN Thread for github issue 378 - Side effects of ssn:Observation being a kind of dul:Event instead of dul:Situation

This seems to be another consequence of the distinction between Observation as record and Observation as event. It makes sense that a record be disjoint with and later in time than a Stimulus (ResultTime vs PhenomenonTime) but if the event of sensing is disjoint with the Stimulus being sensed,  there generally isn’t going to be any result. Therefore, if om:Observation is to be adopted, isPostconditionOf will not be the appropriate relationship between Stimulus and Observation.

—Josh


On Sep 28, 2016, at 9:23 AM, Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>> wrote:

Maxime,

Thank you so much for following up on this.

isPostconditionOf looks ok to me because
-(1) its rdfs:comment annotation says “ Direct succession applied to situations.  E.g., 'Taking some rest is a postcondition of my search for a hotel'.”
-(2) and another reference says  ‘"Direct succession applied to situations. E.g., 'A postcondition of our Plan is to have things settled'."”
-(3) it seems to capture the intended relationship between a stimulus event and an observation. Certainly we would not want that a stimulus causes an observation, nor that an observation is a necessary consequence of a stimulus, but I think we are ok here. It does say that the stimulus comes first, and then the observation, but that seems quite ok too.

Note that the domain and range of isPostconditionOf are both the union of Event and Situation, so no problem there. includesEvent  had a range of Event, so this expansion of the range  to Event or Situation is not going to get existing implementations in to  additional trouble  (ie beyond the trouble already implied by the descision to change Observation).

It is a subproperty of directlyFollows (an intransitive ordering relation)  and an inverse of hasPostcondition.  While these may not have been intended by the original includesEvent (in which the situation of observation just  includes the Stimulus event),  I cannot see any problem in using isPostconditionOf, and indeed it looks to me like the difference in meaning is only the necessary difference that arises to the move of Observation to an Event.

So I’d vote for isPostconditionOf, being the closest match possible to the previous.

--Kerry




From: Maxime Lefrançois [mailto:maxime.lefrancois.86@gmail.com]
Sent: Wednesday, 28 September 2016 6:53 PM
To: SDW WG Public List <public-sdw-wg@w3.org<mailto:public-sdw-wg@w3.org>>
Subject: SSN Thread for github issue 378 - Side effects of ssn:Observation being a kind of dul:Event instead of dul:Situation

Dear all,

If each github issue shall have its own thread on the SDW list, this is the one for issue 378 - https://github.com/w3c/sdw/issues/378 :


if ssn:Observation<http://www.w3.org/ns/ssn/Observation> is a kind of dul:Event<http://www.ontologydesignpatterns.org/ont/dul/DUL.owl#Event> instead of a dul:Situation
there is an immediate side effect to resolve:
axiom:

ssn:Observation rdfs:subClassOf [ owl:onProperty dul:includesEvent ; owl:someValuesFrom ssn:Stimulus ] .
context axioms:

ssn:Stimulus rdfs:subClassOf dul:Event .

dul:includesEvent rdfs:domain dul:Situation ; rdfs:range dul:Event .
solution to solve the side effect:
replace the mention of dul:includesEvent in axiom by a property that has for domain and rangedul:Event
the only such DUL properties are: dul:isPreconditionOf, and dul:isPostconditionOf.
Neither of them seem to fit,
so, should this axiom be simply deleted from the SSN-DUL alignment ?

Kind regards
Maxime Lefrançois