Barry, Pat, All --

Barry wrote...

From my experience working with biologists and medical researchers
on ontologies, definitions (ideally both natural language definitions
and equivalent formal definitions) play a very useful role when it
comes to ensuring that ontologies are populated in consistent ways
across disciplines and subsequently used correctly (or indeed at all)
in practical applications. Most of those involved in such use will
not have logical or computer science expertise. Where else should
they turn to find out what a term means?

It may actually be useful to expand Barry's observation, and also W3C-style "semantics" as follows:

* Semantics1 Is (meta)data semantics, W3C-style

* Semantics2 Specifies what an inferences should be made from any collection of rules and facts -- usually based on a model theory, e.g. as in [3].

* Semantics3 Concerns the real world English meanings of logical predicates

As Barry and Pat may have heard me say before (:-), it seems important, in a practical setting, that the three kinds of Semantics should work seamlessly together.

For example, if Semantics2 is absent, the inferences that are made depend on the whims of the programmers who implement the engine. (SQL is a case in point).

If Semantics3 is absent, as Barry said, practitioners may not even use a system.

It's also necessary to link Semantics2 and 3 computationally in both directions, otherwise authors can't be sure that the system will do what they want. Attempto Controlled English is one approach, and the Internet Business Logic system [1] uses another, uncontrolled approach. The computational linkage allows a system to support English explanations of its reasoning, at the scientific or business level.

For folks who are uneasy about the lack of formal definitions at the English author-user interface, the uncontrolled approach in the Internet Business Logic system allows the English<-->formal linkage to be made explicit, see e.g. [2], which is based on an example from one of Barry's papers.

Cheers, -- Adrian

[1] Internet Business Logic (R)
A Wiki for Executable Open Vocabulary English
Online at www.reengineeringllc.com Shared use is free

[2] www.reengineeringllc.com/demo_agents/RelBioOntDefn3.agent

[3] Backchain Iteration: Towards a Practical Inference Method that is Simple
Enough to be Proved Terminating, Sound and Complete. Journal of Automated Reasoning, 11:1-22

Adrian Walker
Reengineering

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