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opengeospatial / sensorthings

The official web site of the OGC SensorThings API standard specification.
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Compatibility with the Semantic Sensor Network Ontology? #38

Open abourdon opened 6 years ago

abourdon commented 6 years ago

Hi,

Is there a goal to be compatible in the future with the OGC's Semantic Sensor Network Ontology?

Regards, Aurélien

lieberjosh commented 6 years ago

Both are aligned with Observations and Measurements, as is SOS, but not identically. SensorThings Datastream does not exist in SOSA/SSN, but may align with the proposed SOSA:ObservationCollection. SensorThings Thing does not exist in SOSA/SSN and it is unclear how that would be aligned.

There are a number of parts of SOSA/SSN relating to sampling and actuating, as well as procedures, platforms, etc. that are not part of Sensor Things and await specific proposals as to how they might be incorporated.

lieberjosh commented 6 years ago

Thinking about this further, it may be that the best alignment for a SensorThings "Thing" is with SOSA:Platform. This allows commonality of location for some number of Datastreams, Sensors, ObservableProperties, etc. and is relatively agnostic to whether it moves between observations as well as whether observations made from it target the same or different features of interest. Only slightly complicated by the fact that there is no direct connection as in SOSA between Sensor and Thing, only through Datastream. Sosa:Platform could be added as a common property to sosa:ObservationCollection to strengthen this alignment .

lieberjosh commented 6 years ago

Another alignment issue is that not all SOSA relations go through Observation and the proposed SOSA extension sosa:ObservationCollection. A sos:Sensor observes a sosa:ObservableProperty. A sosa:ObservableProperty isPropertyOf sosa:FeatureOfInterest (through ssn:Property). sosa:Platform (isSameAs stapi:Thing ?) hosts sosa:Sensor. Granted that the relation chain through stapi:Datastream can be followed in STAPI, but it does require the existence of an appropriate Datastream in order to do so.

abourdon commented 6 years ago

Thank you @lieberjosh for these remarks. Indeed, both are aligned with Observation perspective but using some minor differences. I'm looking for a way to inject data provided by a SensorThings API system to an SSN/SOSA based ontology.

Indeed, I think we could have these (approximatively) equivalences:

lieberjosh commented 6 years ago

@abourdon, This is quite close. Not sure that stapi:Location aligns with [ssn:forProperty of a ssn:Deployment] since deployment has more to do with attaching a sensor to a platform. May be more appropriate to say that stapi:Thing is both a sosa:Platform and a sosa:FeatureOfInterest, which may have an ObservableProperty equivalent to stapi:Location / stapi:HistoricalLocation. This is what the sosa:Platform example shows.

abourdon commented 6 years ago

@lieberjosh, Even if a sosa:FeatureOfInterest could have a location, I don't know if conceptually a stapi:Thing can be aligned with a sosa:FeatureOfInterest. As wrote in the definition:

Feature Of Interest - The thing whose property is being estimated or calculated in the course of an Observation to arrive at a Result, or whose property is being manipulated by an Actuator, or which is being sampled or transformed in an act of Sampling.

As for SensorThings API, a sosa:FeatureOfInterest is only the entity from which a sosa:Sensor wants to observe a particular sosa:ObservableProperty.

IMHO, to align with SensorThings API, notion of stapi:Location or stapi:HistoricalLocation should be directly correlated with a sosa:Platform. However, there is no similar property that could contain these locations. The best I could find was to use the ssn:isDeployment relation that give a ssn:Deployment from which we use the ssn:forProperty relation to point to a ssn:Property. And regarding the documentation, this ssn:Property could contain our locations:

Property - A quality of an entity. An aspect of an entity that is intrinsic to and cannot exist without the entity.

What do you think?