A Survey of Top-level Ontologies
Approach and Contents
The approach has three parts:
- collect candidate top-level ontologies (2.1)
- develop assessment framework (2.2)
- assess candidate top-level ontologies against the framework (2.3)
These are described in more detail below.
2.1 Collect candidate top-level ontologies
A long list of possible candidates for TLO content that might be useful for the construction of the FDM has been drawn up and reviewed.
Candidate ontologies were identified both through extensive desktop research, and through the experience and domain knowledge of the expert community involved in bringing this report together.
In identifying candidates, the net was thrown as wide as possible to identify as much useful content as possible. Thus, though the focus is on ontological commitment, the list includes data models that are generic in nature (ones without an explicit ontological foundation) as these are likely to have some useful ontological content. The candidates are listed in Appendix D and are available online within the IMF Developers Network on the Digital Twin Hub, www.digitaltwinhub.co.uk.
2.2 Develop assessment framework
In compiling this report, a first-pass assessment framework was developed to facilitate the initial testing of the spectrum of available TLOs and other ontological models against the needs of the programme. This assessment is distinct from the future activities around the further down-selection of TLOs to a selected core for the FDM.
An ontology is (according to Jonathon Lowe in The Oxford Companion to Philosophy) “the set of things whose existence is acknowledged by a particular theory or system of thought.” When we interpret a dataset, working out what the data refers to, we are acknowledging that the dataset commits to these things existing. We are committing to an ontology – making an ontological commitment.
There are a variety of ways of making these commitments. The purpose of a top-level ontology is to enable us to make the choice of ontological commitments in an explicit and consistent way.
There have been a series of attempts to get to grips with the kinds of choices of ontological commitments that ontologies can make. They provide a reasonable starting point but need substantial further work to provide a comprehensive framework for making choices across a broad range of commitments. We have developed a comprehensive choice component for this framework; one that is suitable for assessing information system TLOs.
With this choice component in place, we can look at how these choices shape an ontology’s underlying architecture and so what it can do and how it does it. We can also characterise the candidate TLOs in terms of whether they make a choice and which they choose.
The assessment framework has three levels.
- A general level, which looks at whether the TLO makes an ontological commitment and the strength of this commitment (see 4.1).
- A formal level, which looks at how the formal structure of the TLO has been impacted by its ontological commitment (see 4.2).
- A universal level, which looks at how the TLO addresses the individual universal choices (see 4.3).
Further details on the basis for the assessment process are described in section 4.
2.3 Assessment of candidate top-level ontologies against the framework
The assessment framework described above has been applied to the candidate TLOs. Only a small number of TLOs made their ontological commitments explicit, enabling a clear, simple assessment. In other cases, the choices could be clearly inferred from the documentation available. However, in many cases we could not
determine the choice.
It could be that no choice was intended, or that the choice is not documented, or not documented sufficiently clearly in the material we have reviewed or some other reason. Rather than trying to classify the exact reason for each case, where we have not noted a choice, we have marked the cell ‘not assessed’. In some cases, typically ISO standards, the documentation is not publicly available, so to make this clear we have marked these ‘not available’. The results of the assessment are stored online within the IMF Developers Network on the Digital Twin Hub, www.digitaltwinhub.co.uk. with a summary provided in section 6.
In addition, a brief overview of the candidate top-level ontologies with any useful additional points is given in Appendix F. These include a graphical representation of the TLOs where one has been found. A comparison shows clearly the diversity of top-level structures.
2.4 Terminological note
This is a topic that crosses multiple disciplines, including information systems, computer science, philosophy and linguistics. Confusingly, many terms are used with different senses across these disciplines and even within them. Accordingly, we will attempt, where possible, to use terms with the senses that they have in the disciplines in which they arise – to minimise any increase in the confusion and encourage cross-disciplinary consistency.
There is one critical case where there is little consistency, this is a term for objects in general. These are sometimes also known as entities or things – through all three of these terms have restricted senses in various sub-disciplines. We propose to use the term ‘object’ here, rather than ‘entities’ or ‘things’ unless the context requires it as this is the term most consistently used in philosophy, and can be found with this sense as far back as the 17th century (Locke, 1975). Where needed we will qualify the term – for example, material objects. If we are using the term in a different sense, we will clearly note this. Of course, all three terms will appear in the extracts from the TLO documentation.
Other terms are defined in the glossary in Appendix K.