AIC Seminar Series

Ontologies often define universes of discourse in which the subjects of which the ontologies themselves consist (the "meta-subjects") cannot be represented. The meta-subjects – the subjects implicitly referenced by the expression of the ontology – are comparatively underprivileged; they can’t participate in whatever automated reasoning the ontology was designed to support. This is normal and natural, but it’s inconsistent with any requirement for reasoning in the context of data expressed in terms of multiple ontologies, or for reasoning in terms of one ontology about data that is expressed in terms of another ontology.

Subject-based reasoning over a set of corpora in which each corpus is governed by a different, independently-conceived and maintained ontology, can be significantly facilitated by providing seamless access to all the various statements about each subject. The key to achieving such seamlessness is to recognize whenever any two parts of any corpora reference the same subject, and to provide a single locus – a single "subject proxy" – for that subject. From that single subject proxy, everything that invokes its subject can be made directly available. In effect, a subject itself, as opposed to any specific statements about it, or even any particular way of uniquely identifying it, becomes a wormhole that interconnects the universes of discourse in which statements about the subject have been made. Such a wormhole exists whenever a subject proxy is the locus of multiple statements that are governed by distinct ontologies. The proxy’s single subject is known to exist simultaneously in the distinct universes of discourse defined by the distinct ontologies.

To the extent that time permits, we’ll think about an ontology in terms of the subjects of which it consists, ie, meta-subjects, how to represent those meta-subjects using subject proxies, and how to use this representation for subject-based reasoning.

Steve Newcomb is a consultant with Coolheads Consulting (www.coolheads.com), which provides information management consulting and topic map production services to an international clientele that includes U.S. government agencies. He is the author of the open-source "Versavant" subject map pattern engine (www.versavant.org). He serves as co-editor of the Topic Maps International Standard, ISO/IEC 13250 (www.isotopicmaps.org). He co-chairs the Extreme Markup Languages conference (www.extrememarkup.com).

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