Alignment to O&M
Proposal for text relating to O&M alignment, per ACTION-255.
8. Alignment to Observations and Measurements
This section is normative.
This section introduces the alignment of SOSA/SSN to OGC Observations and Measurements [OandM] (also known as ISO 19156:2011). The XML implementation of O&M [OM-XML] is used for the payload for SOS services, of which there are many operational deployments. Integration of these with observation data formalized using SOSA and SSN is highly desirable, and would be expected to significantly enrich the set of resources represented using SOSA/SSN. The alignment presented here provides a basis for transforming OM-XML data into RDF or OWL individuals according to the SOSA/SSN ontologies.
Identifying the UML elements
O&M is specified as a UML model, following the patterns specified in ISO 19109 Geographic Information - Rules for Application Schema [ISO-19109]. This means that the classes represent concepts from the application domain, so can be approximately equated with classes in an ontology.
An OWL implementation of O&M may be generated by explicit translation of the UML following rules specified in [ISO-19150-2] - see [OM-Heavy]. This translation generates an RDF entity denoted by a URI for every class, class attribute, and association-role from the original O&M UML model. The form of the URIs is also specified in [ISO-19150-2], and appear explicitly in the official OWL implementation of ISO 19156 (O&M) maintained by the ISO/TC 211 Group on Ontology Management. These URIs are therefore convenient identifiers for elements of the O&M in a formal alignment.
The explicit translation from the UML comes at a cost of a large set of dependencies on similar OWL translations of other UML models from ISO 19100 series standards. Furthermore, the ontology structure reflects artefacts of the UML-style of modeling. This implementation may introduce entailments that are inconsistent with SOSA/SSN (though no inconsistencies have been identified yet) so it is important to understand that use of these URIs here are principally intended to denote the original UML classes and properties, rather than this OWL implementation.
NOTE: In response to the complexity of the explicit translation, a handcrafted version in more idiomatic OWL, without the dependencies, is also available [OM-Lite].
NOTE: At time of writing, the ISO-specified URIs do not de-reference, however, ISO/TC 211 are currently developing a publication system to enable this and thus the use of these URIs as Linked Data.
The following namespace prefixes are used in the alignment to SOSA.
Five utility classes are defined locally to support the formalization of the alignment.
1. Three disjoint subclasses of sosa:Procedure:
|sosa-om:ActuationProcedure||Actuation procedures or recipes|
|sosa-om:ObservationProcedure||Observation procedures or recipes|
|sosa-om:SamplingProcedure||Sampling, sample preparation or processing procedures or recipes|
2. Two classes related to sampling, which complement SOSA classes related to actuation and observation:
|sosa-om:SamplingDevice||Sampling, sample preparation or processing devices, comparable to sosa:Actuator and sosa:Sensor|
|sosa-om:SamplingEvent||Sampling, sample preparation or processing event or act, comparable to sosa:Actuation and sosa:Observation|
The primary classes from [OandM] have direct equivalents in SOSA classes supplemented by the utility classes described above, as follows:
|iso19156-om:OM_Process||equivalent class||Union of ( sosa:Sensor or sosa-om:ObservationProcedure )|
|iso19156-sf:SF_Process||equivalent class||Union of ( sosa-om:SamplingDevice or sosa-om:SamplingProcedure )|
Additional alignments from SOSA/SSN classes to O&M classes are as follows.
where iso19156_gfi:GFI_DomainFeature has the definition:
- The class GFI_DomainFeature represents 'real-world' features which are the ultimate subject of an observation campaign, i.e. the features from an application domain that are not artefacts of the observation process (sampling features).
sosa:FeatureOfInterest is a subclass since not all domain features are subjects of observation.
where iso19156_gfi:GFI_Feature has the definition
- The class GFI_Feature represents the set of all classes which are feature types. In an implementation this abstract class shall be substituted by a concrete class representing a feature type from an application schema associated with a domain of discourse (ISO 19109, ISO 19101).
The following properties from [OandM] have direct equivalents in SOSA properties:
Additional alignments from O&M properties to SOSA are as follows.
These are modeled as sub-properties because sosa:usedProcedure, sosa:hasResult and sosa:resultTime applies to actuation, observation or sampling activities.
This is modeled as a sub-property because the domain of iso19156-sfs:SF_SpatialSamplingFeature.hostedProcedure is a spatial sampling feature, such as a station, rather than a more general platform.
An RDF file containing a graph corresponding to this alignment is available.