First a W3C Definition:
The RDL (Reference Data Library) lists the concepts (Classes) in above definition in a taxonomy. That taxonomy has the entity types of the data model of ISO 15926-2 as the top. Below that are their specializations, as applicable to the Process Industries.
In this topic the (to-be-establisched) Reference Ontology, covering the "relationships" in above definition, is outlined. These relationships come in the form of ISO 15926-7/8 Template instances.
DiscussionBefore getting lost in the details it makes sense first to show how the classes are arranged in the ISO 15926-2 data model. For this the diagram from the topic "How does P101 fit in?" is used:
We can define ontologies in five levels:
This is shown in the diagram below, showing an example of a centrifugal pump and its impeller(s):
The rounded-off blocks are Relationships or ClassOfRelationships, where the latters define the semantics of the ontologies. Keep in mind that there are many different types of relationships.
Sticking to this example we can think of the following for the five ontologies:
ExegesisFor any occurrence of PossibleIndividual the following information applies:
When it is an ActualIndividual
ExamplesThe examples given below follow the diagram.
Metaclass UO of ISO 15926-2
SUBTYPE OF (class_of_arrangement_of_individual);
is a specialization of ClassOfArrangementOfIndividual
SUPERTYPE OF (ONEOF(class_of_feature_whole_part, class_of_assembly_of_individual, namespace))
SUBTYPE OF (class_of_composition_of_individual);
which is a specialization of ClassOfCompositionOfIndividual:
SUPERTYPE OF (ONEOF(class_of_arrangement_of_individual, class_of_temporal_whole_part, class_of_participation))
SUBTYPE OF (class_of_relationship);
class_of_part : class_of_individual;
class_of_whole : class_of_individual;
It has two relations, classOfPart and classOfWhole, that both have an instance of ClassOfIndividual as rdfs:object (i.e. points at the URI of that instance).
This is ISO standard, cast in concrete.
Class UO of ISO 15926-2
The AssemblyOfIndividual relationship
SUBTYPE OF (arrangement_of_individual);
is a specialization of ArrangementOfIndividual
SUPERTYPE OF (ONEOF(assembly_of_individual, feature_whole_part))
SUBTYPE OF (composition_of_individual);
SELF\composition_of_individual.whole : arranged_individual;
END_ENTITY;which is a specialization of CompositionOfIndividual:
SUPERTYPE OF (ONEOF(arrangement_of_individual, temporal_whole_part, participation, temporal_bounding))
SUBTYPE OF (relationship);
part : possible_individual;
whole : possible_individual;
This is ISO standard as well, cast in concrete.
Reference Ontology of ISO 15926-4The example shown in the diagram is that any member of the ClassOfInanimatePhysicalObject CENTRIFUGAL PUMP has one-to-many members of the ClassOfInanimatePhysicalObject IMPELLER.
This can be represented with the following specialization of the ISO 15926-7 Template ClassOfAssemblyDefinition:
ont:CentrifugalPumpAssembly-001 rdf:type lci:Template ;
rdfs:subClassOf tpl:ClassOfAssemblyDefinition ;
rdfs:label "[ONE TO ONE] member(s) of [PUMP] class [CENTRIFUGAL PUMP] have [ONE TO MANY] member(s) of [IMPELLER] class [PUMP IMPELLER] as parts in an assembly"@en ;
tpl:hasClassOfWhole rdl:RDS416834 ; # CENTRIFUGAL PUMP
tpl:hasClassOfPart rdl:RDS816299 ; # PUMP IMPELLER
tpl:hasDefined :36fbed7d-21b3-4543-9402-d20c8e8ace79 ;
tpl:hasCardinalityOfWhole rdl:RDS999900701 ; # ONE TO MANY
tpl:hasCardinalityOfPart rdl:RDS222625 ; # ONE TO ONE
meta:valEffectiveDate "2021-02-14T00:00:00Z"^^xsd:dateTime .
Some notes to this:
Keep in mind that the pumped Stream class is not included above.
As can be understood, setting up ontologies like this for all equipment types requires a serious investment, but it will provide a far better communication between all parties involved in the industry. It will be an essential prerequisite for powerful engineering, bid evaluation, and inspection software.
Each piece of information is a Class of which many Individuals can be a member. For example, the temperature of 37° C is 'possessed' by billions of people, and the material of construction applies to many artefacts. This means that an Individual that possesses a temperature of 37° C is a member of that Class. The rationale of the authors of ISO 15926-2 was, and is, that a property is a class of individuals possessing that property.
So, the instance of ClassOfInanimatePhysicalObject called CENTRIFUGAL PUMP is the intersection of all applicable characteristics Classes, as defined on a technical specification, like in this case the API 610 Data Sheet for Centrifugal Pump. This intersection can be modeled by making all template instances members of an instance of EnumeratedSetOfClass.
NOTE - In the context of CFIHOS this ontology is a specialization of their Tag Class with Tag Class Properties.
Product Model Ontology
This is, for each product model of a manufacturer, an ontology like the Engineering Ontology, be it for classes with a far larger membership. The Stream-related characteristics are different, because based on standard conditions.
For plant information the specialized Product Model Ontology, marked with  in the Plant Lifecycle Model, is useful.
NOTE - In the context of CFIHOS this ontology is about their Model Part with Model Part Properties, and a specialization of their Equipment Class with Equipment Class Properties.