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What is an instance of ssn:Property

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What is an instances of ssn:Property ?

Resolution: added a section 7.4 Generic or Specific Instances of ssn:Property in the section Common Modeling Questions of the specification.

What is an instances of ssn:Property ?

Objective: see in the datasets that are referenced at http://w3c.github.io/sdw/ssn-usage/ what are the instances of ssn:Property.

Definitions

In oldSSN: An observable Quality of an Event or Object. That is, not a quality of an abstract entity as is also allowed by DUL's Quality, but rather an aspect of an entity that is intrinsic to and cannot exist without the entity and is observable by a sensor.

In sections in https://www.w3.org/2005/Incubator/ssn/XGR-ssn-20110628:

5.3.1.2.4 Observed Properties: Properties are qualities that can be observed via stimuli by a certain type of sensors. They inhere in features of interest and do not exist independently. While this does not imply that they do not exist without observations, our domain is restricted to those observations for which sensors can be implemented based on certain procedures and stimuli. To minimise the amount of ontological commitments related to the existence of entities in the physical world, observed properties are the only connection between stimuli, sensors, and observations on the one hand, and features of interests on the other hand.

5.3.1.3.4 Observed Properties: ObservedProperty is defined as a subclass of DUL:Quality. Types of properties, such as temperature or pressure should be added as subclasses of ObservedProperty instead of individuals. A new relation called SSO:isPropertyOf is defined as a subrelation of DUL:isQualityOf to relate a property to a feature of interest.

5.4.3.6 Wind Feature and properties: This example also includes a definition for Wind as a Feature of Interest with two properties: wind direction and wind speed.

Usage in referenced Datasets

PREFIX ssn:  <http://purl.oclc.org/NET/ssnx/ssn#>
SELECT DISTINCT *  WHERE {
 { ?prop a ssn:Property } 
 UNION {?sensor ssn:observes ?prop }
 UNION {?obs ssn:observedProperty ?prop }
 UNION {?foi ssn:hasProperty ?prop }
} LIMIT 100

D3:

D4:

D5:

D10

SSN Extension in SEAS core ontology seas:FeatureOfInterest

The following RDF Graph describes a fridge, with its property <fridge/1/consumption>: 

<fridge/1> a seas:FeatureOfInterest ;
 seas:hasProperty <fridge/1/consumption> .

One can further define the semantics of this property by refining the relationship it has with <fridge/1>. This is done using sub properties of seas:hasProperty, informally named property keys, that are functional properties with domain seas:FeatureOfInterest and range seas:Property. For example, 

ex:consumption a owl:ObjectProperty , owl:FunctionalProperty ;
 rdfs:subPropertyOf seas:hasProperty ;
 rdfs:domain ex:ElectricPowerSystem ;
 rdfs:range ex:EnergyProperty .

Then the link between <fridge/1> and property <fridge/1/consumption> can be further specified: 

<fridge/1> a seas:FeatureOfInterest ;
 ex:consumption <fridge/1/consumption> .

Conclusion

  • D3, D10, SEAS, are conformant with the definitions of ssn:Property
  • D4 and D5 are not, because the instances of ssn:Property are generic and are not bound to a feature of interest
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