Introduction

This is about Property, IndirectProperty and IndividualDimension, and the misunderstandings around them.

IndirectProperty

ISO 15926-2 has a rather strange entity type: the IndirectProperty, which is defined as follows:

	An indirect_property is a relationship between a property and a possible_individual. The nature
	of the indirect_property is defined by its classification by a class_of_indirect_property.

	A property is indirect when it does not apply directly to the possible_individual to which it applies,
	but is derived from some process.

	NOTE A property is indirect because it does not directly apply. There can only be one temperature that a thing
	has (at a time), so a Maximum Allowable Working Temperature is not its temperature, but an indirect property
	derived from doing some tests or calculations to determine its value (as opposed to it being a current
	measurement). This is what makes it indirect.

The rationale in the NOTE is a bit strange, because for the same token I can say: my feet are usually colder than my head, so I have more than one temperature. Moreover, there can only be one Maximum Allowable Working Temperature that a thing has (at a time). The point is that a model can be made so precise that it renders useless. There are simply too many situations where it is unclear whether you can, in principle, measure a property or not, and that is not good for the retrieval of information, as is the goal of ISO 15926.

IndividualDimension

This also is confusing. Diameter is such a thing. It is, according to Part 2, a specialization of a Property. As such that is so, diameter is a length, but when I say a diameter of 1.5 metres, no engineer would misunderstand that.

Proposal

I propose to introduce QuantifiableProperty as a replacement for Property, IndirectProperty and IndividualDimension.

I also propose to avoid making, for example, Maximum Allowable Working Temperature a specialization of Temperature, because that is simply physically wrong.

QualitativeProperty

In CFIHOS we see the qualitative property, which appears to have been used so far as a kind of container for everything else. From a proper modeling perspective this is harmful and poor modeling practice. For the most their property picklist values are Classes, so apparently they see classification and specialization as qualitative property. ISO 15926 does not need that.

Use of QuantifiableProperty

An instance of (a subtype of) PossibleIndividual, e.g. P-101, is classified with an instance of QuantifiableProperty, e.g. CAPACITY(volume flow rate) that is quantified as 10.7 on a Scale of m3/hr. Matthew West used to circumscribe 'temperature' as 'a degree of hotness', so not yet quantified.

An instance of (a subtype of) ClassOfIndividual, e.g. the Asset Requirements Class CO-P-101 (CO=ClassOf), is specialized from above instance of QuantifiableProperty.

When a QuantifiableProperty is quantified, it turns into a quantitative property, but not as a Part 2 entity type. The reason why CFIHOS has the concept of quantitative property is because that is the name of the table, and that table has attributes for value and scale.

Even ChatGPT got confused!