ISO 15926 TUTORIAL - LESSON 2 - Upper Ontology for Metaclasses

As planned I will tell you some about ISO 15926-2, the result of 12 years of data modeling work under the lead of (late) Matthew West of (then) Shell HQ in London.
Jan Sullivan and myself worked with Matthew, pulling together the work that many others have contributed. In December 2003 it reached ISO International Standard status.

I have worked with it ever since and, except for a few things, it has proven to be rock stable.

The top of the model is shown in this picture (the links are subClassOf and the '1' is a ONEOF):



Instances of PossibleIndividual or its specializations are you and me and your laptop and your car etc, things that exist.

AbstractObjects do not exist in space-time.

Instances of Class are groups of things that share one or more characteristics, they have 'criteria for membership', like the body weight range of 63.50 - 66.67 kg is the criterium for a membership of the Welterweight Boxer class, and that membership is determined just before a match during the 'weigh-in'. In case he is too light or too heavy there is no match, because he doesn't meet the "criteria for membership".

Instances of Relationship are something unusual for RDF adepts. They are classes (in the general sense of set theory, so not Class in the ISO 15926 sense) that have two unary relations that point at two things that are mutually related, and defined for a particular type of Relationship. The RDF folks call that a reification, in ISO 15926 it is a class in its own right.

Instances of MultidimensionalObject are, from a modeling point of view, a bit odd-ball, but were necessary to be able to create lists, a kind of n-ary Relationship.
It is the basis for Templates, where Template is a subclass of ClassOfInformationRepresentation (a subclass of Class) AND of MultidimensionalObject.

But there is more in the ISO 15926-2 upper ontology, and I captured that in the document called 'ISO 15926 on a page.

A high-level overview of that document is shown below:


The seven parts will be discussed separately, starting with:.

Upper Ontology for Metaclasses


Note that the symbol with ClassOfAssemblyOfIndividual* is a specialization of ClassOfAssemblyOfIndividual.
The objects of the relations classOfWhole and classOfPart of the former are specializations of those of the latter.

This diagram is a simplification of a lot of classes, relationships, and templates, but in essence the structure is as shown above. It covers:

There are more sublasses of ClassOfPhysicalObject, like ClassOfMolecule, but it is advisable not to use these as objects for which you build an ontology.
But if you insist, you can do that. It has to do with the scale of things, macro vs micro.

Combining Part 2 entity types

An example:


that says that members of ClassOfIndividual are defined with members of ClassOfInformationRepresentation. That tilted double-square is the symbol for a ClassOfRelationship (see 'Symbols for graphs').

So, for example (in Lesson 3), the model BMW S3 SE Pro, a specialization(subclass) of CAR, is defined by its product specification, as detailed here. But of course there are much simpler definitions.

That BMW S3 SE Pro is a class, of which your car is a member. That BMW S3 SE Pro is an instance of ClassOfInanimatePhysicalObject, where the latter is called a 'metaclass', that is defining a class in general.

The words 'instance' and 'member' often are used interchangeably. There is a subtle difference:
  • Something is, in essence, an instance of an entity type, (John Dow is a Person)
  • Something is, in most cases temporarily, a member of a class. (John Doe is an Engineer)
although in RDF and OWL both are covered by rdf:type
Another example:


that says that the members of ClassOfDirectConnection relate members of ClassOfIndividual when they are directly connected. The kinds of direct connection, e.g. FLANGED CONNECTION, are defined in the Reference Ontology. Here we deal with the 'grammar' only.

One remark that most of you are well aware of:

Members of a subclass are also members of the applicable superclass(es), where the subclass has the characteristics of its superclass plus some to differentiate itself from that superclass.
Members of a class do not inherit the characteristics (criteria for membership) of that class, but must comply with those criteria for membership in order to be a member.

A thing is deemed to be a member of a class iff its chararceristics comply with the 'criteria for membership' of that class.

In the industry that compliance often is an engineering decision. An oversized pump may comply, but may not if that leads to unacceptable power consumption or process offsets.

If a chemical product does not comply with the applicable standard, it is called 'off-spec'.

Next lesson we will look at the Ontology for Individuals and their relationships to the Ontology for (meta)Classes discussed here.