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

A FRESH IDEA TO SOLVE THIS

Are we just being a little too precious here?
Referring to the 2013 spec for O&M  10-004r3 copied in here – is this the right one please? Note that it post-dates ssn.

4.11
observation
act of measuring or otherwise determining the value of a property
4.12
observation procedure
method, algorithm or instrument, or system of these, which may be used in making an observation
4.13
observation protocol
combination of a sampling strategy and an observation procedure used in making an observation
4.14
observation result
estimate of the value of a property determined through a known observation procedure
.
.
4.17 sampling feature
feature which is involved in making observations concerning a domain feature


This is already self-inconsistent. It does say observation is an “act” (but not an ‘activity’, nor an “event’).
Further,  a procedure is used in making an observation, that is, in making the act of measuring. Really?
And an observation protocol is also used in making an act of measuring. Really?
A sampling feature is  involved in making  acts of measuring?


Later,
An observation is an act associated with a discrete time instant or period through which a number, term or
other symbol is assigned to a phenomenon [2]. It involves application of a specified procedure, such as a
sensor, instrument, algorithm or process chain. The procedure may be applied in-situ, remotely, or ex-situ with
respect to the sampling location. The result of an observation is an estimate of the value of a property of some
feature.

Take away the word  “act” and the same can be said of ssn:observation.
It is uncoincidentally very similar  to the definition of an ssn:observation:

An Observation is a Situation in which a Sensing method has been used to estimate or calculate a value of a Property of a FeatureOfInterest.  Links to Sensing and Sensor describe what made the Observation and how; links to Property and Feature detail what was sensed; the result is the output of a Sensor; other metadata details times etc.

Back to the O&M spec:
-This is a consequence of the fact that an observation is a kind of ‘event’ so…
-Aside from the result, the details of the observation event are….
-Observations focus on the data collection event. An act of Observation serves to..
-An observation event is clearly…

This kind of confusion is what you see without an upper ontology, and it really  doesn’t matter at all until you need an upper ontology. It does O&M no harm.
But ssn uses an upper ontology and *is* careful.


KEY POINT
I can see no formal/interoperability/implementation/codebase  difference whatsoever to the O&M spec if an Observation were not an “act” but instead were some kind of object or information entity as ssn sees an Observation. There is no reason at all why an O&M observation has to be a prov:Activity which is, already different to an “act” as in the spec.  The already inconsistent English text in the spec could be improved, though.

THEREFORE
We should indeed align  ssn:observation with an o&m observation  concept, but  do this by defining o&m:observation to be a record of an event.  This requires us to do nothing at all, there is no issue with prov, no issue with the long-standing dul alignment, no consequence for the SSN  user base, no consequence for the O&M user base.  In our o&m alignment we can explain this choice. TOO EASY.

WHY NOT?

The only argument I am aware of against this solution  is Jeremy’s typing on the F2F IRC :
I think ... For me, it seems natural to treat Observation as an Activity ... it's something that's done at a particular time using a specified process. It produces a some data (the result) ... the data, an information resource, is an Entity. SSN seems unnecessarily complex in splitting the problem into SensorOutput, Observation and ActivityOfSensing; OM does this in two classes: Result and Observation.

Well, if it is “natural” then why is the spec so confused about it?  “unnecessarily complex”: is a furphy(!)  – there is no ActivityofSensing in ssn. Having said that, I expect Jeremy is not alone in expecting an observation to be something like an  activity.


-Kerry



From: Kerry Taylor [mailto:kerry.taylor@anu.edu.au]
Sent: Saturday, 8 October 2016 11:22 PM
To: Simon.Cox@csiro.au
Cc: 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

So I missed some of these remarks  in my reply a moment ago --- but I still hear that we have no choice other than “isPostconditionOf” to replace includesEvent. Remember that this is only in the dul alignment, not in ssn proper, and is therefore  non-normative.

As a quite separate issue, I think I hear a call for expanding the definition of ssn:Sensor” to include prediction ?  Assuming we are happy with the relationship to ssn:Stimulus, I can’t see any problem with this as it would only affect annotation properties and  is a widening, rather than narrowing, of the concept.

But I will not propose it --- I don’t have a need for it.

-Kerry

From: Simon.Cox@csiro.au<mailto:Simon.Cox@csiro.au> [mailto:Simon.Cox@csiro.au]
Sent: Friday, 7 October 2016 5:50 PM
To: jlieberman@tumblingwalls.com<mailto:jlieberman@tumblingwalls.com>; janowicz@ucsb.edu<mailto:janowicz@ucsb.edu>
Cc: Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>>; maxime.lefrancois.86@gmail.com<mailto:maxime.lefrancois.86@gmail.com>; 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

I like that. I think it addresses my original concern nicely.
Though I think I would adjust the naming to ‘stimulusTime’ vs ‘phenomenonTime’ (the latter is still the time that most users care about and preserves the current semantics).

if the stimulus-time is omitted it is assumed to be the same as phenomenon-time?

From: Joshua Lieberman [mailto:jlieberman@tumblingwalls.com]
Sent: Thursday, 6 October 2016 9:02 PM
To: janowicz@ucsb.edu<mailto:janowicz@ucsb.edu>
Cc: Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au<mailto:Simon.Cox@csiro.au>>; kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>; maxime.lefrancois.86@gmail.com<mailto:maxime.lefrancois.86@gmail.com>; 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

Jano,

1) I think you mean manometer, which depends on the density of mercury, not its compressibility. Different stimulus.

2) As long as it is clear that the stimulus time has to overlap the measurement time at least in part.

3) Pondering further, I think it makes more sense for a prediction to estimate an observable property in the future based on present stimulus / stimuli (related to that property by a model). This does carry the implication that some other, more contemporaneous stimulus would also occur in the future if appropriate, but that stimulus would not be a result of the predictive observation. Instead it would be the stimulus for another observation that also takes place in the future and results in another, validating estimate of the observable property. This should work pretty well to represent both present and future estimates, however, it will take some elaboration of the time parameters, namely differentiation of PhenomenonTime from ObservablePropertyTime.

Josh

On Oct 5, 2016, at 5:46 PM, Krzysztof Janowicz <janowicz@ucsb.edu<mailto:janowicz@ucsb.edu>> wrote:

IMHO, /Stimulus/ is best conceptualized as  detectable changes in the environment that trigger the observation process. In 2010 (for the SSO) Michael and I wrote:

"Stimuli are detectable changes in the environment, i.e., in the physical world. They are the starting point of each measurement as they act as triggers for sensors. Stimuli can either be directly or indirectly related to observable properties and, therefore, to features of interest. They can also be actively produced by a sensor to perform observations. The same types of stimulus can trigger different kinds of sensors and be used to reason about different properties. Nevertheless, a stimulus may only be usable as proxy for a specific region of an observed property. Examples for stimuli include the expansion of liquids or sound waves emitted by a sonar. The expansion of mercury can be used to draw conclusions about the temperature of a surface that is in close contact. While the expansion is unspecific with respect to the kind of surface, e.g., water versus skin, the usage as stimulus is limited by its melting and boiling points. Moreover, mercury is not restricted to thermometers but e.g., also used in nanometers. Note, that the stimulus is the expansion of mercury, not mercury as such.”

1)

The last sentence (and assuming this definition is still valid/acceptable for our current work), is the most important one. A stimulus is an event (if we really, really, really want to use these terms). The stimulus also has to start before the observation can take place. Multiple possible temporal relations can hold between the two. for instance, the mercury in the text above will shrink after an measurement procedure (resulting in an observation) is executed. This will (or will not) keep triggering a sensor but we stopped caring because we arrived at the observation we anted to archive.

2)

I like Josh's idea about predicting future stimuli but would suggest not to mix this with the notion of an observation. Predictions about the future are not observations in the sense we use in the SSN; if they are, they are predictions based on observations which in turn are based on stimuli that we consider good proxies for the stimulus we want to predict :-).

3)



Best,
Jano



On 10/03/2016 08:36 PM, Joshua Lieberman wrote:
I do mean (topologically not logically) disjoint in time, i.e. non-overlapping. If “isPostConditionOf” carries a strict temporal meaning, then it breaks the relationship between stimulus and observation. You can’t measure a temperature if the temperature has gone away before you measure it. If the meaning is only consequential, in the sense of observation O→stimulus S, then it would be a reasonable predicate. Still tricky for prediction, i.e. to assert that a stimulus in the future is a consequence of a prediction in the present. I suppose one could indicate in some way that it's a weaker consequence.

One could also argue that an observation that overlaps its stimulus in time is a measurement, while an observation that doesn’t overlap its stimulus is a prediction. A model procedure can predict the past, the present, or the future, or none of the above if the model conditions are hypothetical. It is going to require some more thought, though, to figure out how to apply the SSN / O&M terms to this situation. Is a prediction just another procedure within an observation, or is a prediction a different type of event (e.g. a model run) that generates an imaginary / potential observation?

—Josh


On Oct 3, 2016, at 1:31 PM, simon.cox@csiro.au<mailto:simon.cox@csiro.au> wrote:

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<mailto:jlieberman@tumblingwalls.com>>
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

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




--

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/


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