Adding membership relationships to ISO 15926-2 in OWL

Status of this document: Sketch

Author:

• Martin G. Skjæveland, DNV

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Table of Contents

1. Abstract
2. Introduction
3. OWL representation
4. Identified membership relationships in ISO 15926-2
5. Candidate membership relationships in ISO 15926-2

Abstract

This article suggests a formalization of the membership relationships expressed more or less informally in the text definition of the entity types of ISO 15926-2:2003 and how they may be expressed in OWL.

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Introduction

ISO 15926-2 defines a quite substantial hierarchy of membership relationships. An example of one such sub hierarchy is the following:

A class_of_class_of_individual is a class_of_class whose members are instances of class_of_individual. (ISO 15926-2:2003, p. 166)

A class_of_individual is a class whose members are instances of possible_individual. (ISO 15926-2:2003, p. 117)

Figure 1: An example of a membership hierarchy. #TheOldPumpInMyGarage is a member of PUMP, PUMP is a member of ROTATING MECHANICAL EQUIPMENT CLASS. ROTATING MECHANICAL EQUIPMENT CLASS is an instance of class_of_class_of_individual, PUMP is an instance of class_of_individual and #TheOldPumpInMyGarage is an instance of possible_individual.

However, this hierarchy is not included in the EXPRESS listing of ISO 15926-2 due to what seems to be lack of expressiveness in the EXPRESS language: "It should be noted that the EXPRESS subtypes of class defined in this part of ISO 15926 are instances of class_of_class, though the EXPRESS language specification does not allow this to be stated" (ISO 15926-2:2003, p. 37). This information is naturally therefore not included in the OWL representation of the EXPRESS file. (Read more: ISO15926inOWLtranslateEXPRESStoOWL.) The membership relation/(Classification) is together with the specialization relation the most fundamental way to describe the universe of interest. Capturing this information is thus important to ensure that the ISO 15926-2 data model is used as intended.

OWL representation

The membership relation is represented in ISO 15926-2 using the entity type CLASSIFICATION: classification is a relationship that indicates membership of a class (ISO 15926-2:2003, p. 33). The OWL definition of CLASSIFICATION in the OWL file http://rds.posccaesar.org/2008/02/OWL/ISO-15926-2_2003 is the following

Class: Classification
    SubClassOf: 
        Relationship,
        hasClassifier exactly 1 Class,
        hasClassified exactly 1 Class

The EXPRESS definition is found here: classification.

[diagram]

The owl:ObjectProperties hasClassified and hasClassifier is defined in ISO 15926-2 OWL as

ObjectProperty: hasClassifier
  Domain: 
    Classification

ObjectProperty: hasClassified
  Domain: 
    Classification

We want to put local restrictions on the use of Classification on specific entity types, e.g., such as (informally) "a ClassOfIndividual may only have PossibleIndividual-s as members". To be able to do so we need to define the inverse ObjectProperies of hasClassifier and hasClassified, respectively isClassifierIn and isClassifiedIn:

ObjectProperty: isClassifierIn
  Inverses: 
    hasClassifier

ObjectProperty: isClassifiedIn
  Inverses: 
    hasClassified

This allows us to state that "a ClassOfIndividual may only be a classifier in a Classification which has a PossibleIndividual as classified" and "a PossibleIndividual may only be classified in a Classification which has a ClassOfIndividual as classifier", in OWL:

Class: part2:ClassOfIndividual
  SubClassOf: 
    isClassifierIn only (part2:hasClassified only part2:PossibleIndividual)
    
Class: part2:PossibleIndividual
  SubClassOf: 
    isClassifiedIn only (part2:hasClassifier only part2:ClassOfIndividual)

Identified membership relationships in ISO 15926-2

Candidate membership relationships in ISO 15926-2

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