Working on a definition of "ontology"
Hello-
We haven't seen much traffic on this list in a while. We know this topic has probably been debated to death. However, we have given a lot of though to this problem, especially when trying to apply the terminological methods and methodology of ISO TC37 (Terminology).
We've heard the term "ontology" used in many ways and we're thinking about how this is used in the information technology sense, i.e., the kinds of things we talk about here when we speak of "ontology".
We've looked at a couple well-known definitions, such as:
- specification of a conceptualisation of a knowledge domain. An ontology is a controlled vocabulary that describes objects and the relations between them in a formal way, and has a grammar for using the vocabulary terms to express something meaningful within a specified domain of interest. The vocabulary is used to make queries and assertions. Ontological commitments are agreements to use the vocabulary in a consistent way for knowledge sharing. ...
The "specification" part seems problematic. A specification of X, inherently, is about identifying a class of objects that satisfy certain criteria. So a "specification of a conceptualization" means that someone is identifying one or more conceptualizations that meet certain criteria.
In the end, this doesn't address anything computable, which is something we see as essential to "ontology" -- at least the use of "ontology" in the IT sense.
- Ontologies resemble faceted taxonomies but use richer semantic relationships among terms and attributes, as well as strict rules about how to specify terms and relationships. Because ontologies do more than just control a vocabulary, they are thought of as knowledge representation. The oft-quoted definition of ontology is "the specification of one's conceptualization of a knowledge domain."
Then "ontologies" according to this definition are no different than "concept systems", as defined by ISO TC37. TC37's concept systems have relationships among concepts (with no particular requirements on their simplicity or complexity), so the description above is equivalent to TC37's "concept system" ... and if "ontologies" are only "concept systems" then we should call them as such, but we believe there is more.
- Ontology is the newest label attached to some KOSs. Ontologies are being developed as specific concept models by the Knowledge Management community. They can represent complex relationships between objects, and include the rules and axioms missing from semantic networks. Ontologies that describe knowledge in a specific area are often connected with systems for data mining and knowledge management.
We agree somewhat with this definition because there is clearly the computational component to it. All "knowledge organization systems" are TC37 "concept systems" (these KOS might have more than TC37 requires in its definition). And the "rules and axioms" imply some thought towards computation, as evidenced by the reference to "often connected with systems for data mining and knowledge management".
So in conclusion, we have found the following definition to be a reasonable definition that is reasonably precise:
[context: information technology]
ontology: concept system and its computational model
With the above definition, taxonomies and knowledge organization systems all could be ontologies, as long as they include their computational model. For example, a taxonomy of objects in the field of X is just a concept system, but a taxonomy of objects in the field of X that includes a computational model (e.g., producing common/differing characteristics, finding lowest nodes with common features, etc.) could then be an ontology. Whether the computational model is expressed in procedural code (e.g., programs) or non-procedural code (e.g., axioms and statements) is irrelevant.
We'd like feedback on this. We're working on this in INCITS/L8 (the US metadata standards committee) and its corresponding ISO committee ISO/IEC JTC1 SC32 WG2 Metadata.
If you have some improvements to suggest, please feel free to contact us (put "ontology" in the Subject line). Naturally, this can all start a flame war -- no one has the time for this.
Thank you in advance for your comments.
Frank Farance (Farance Inc.)
Dan Gillman (Bureau of Labor Statistics)
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Frank Farance, Farance Inc. T: +1 212 486 4700 F: +1 212 759 1605
mailto:frank@farance.com http://farance.com
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