In a conference call for the forthcoming Ontology Summit, Barry Smith,
Chris Partridge, Anatoly Levenchuk, and Mike Bennett presented four
thoughtful and well organized talks. Following is the summary with
pointers to the slides and the audio recordings: (01)
http://ontolog.cim3.net/cgi-bin/wiki.pl?ConferenceCall_2013_02_07 (02)
On the whole, the presentations were good. But none of them mentioned
four *extremely* important points: (03)
1. Trillions of dollars have been invested in legacy software that
runs the world economy. (04)
2. That software will not be replaced for a long, long time. In past
experience, the lifetime of a large, mission-critical system can be
40 years or more. Its replacements must interoperate with it in
as smooth a transition as possible. (05)
3. Every attempt to replace a critical, working system with a new
one that could not interoperate during the transition has failed.
The greater the discontinuity, the greater the ensuing disaster. (06)
4. Every successful introduction of new technology interoperates with
the interfaces, infrastructure, and conventions of the old system
during an extended, incremental, and evolutionary transition.
The duration of that transition is usually *decades*, not years. (07)
There was some discussion of these issues in the email list for the
ontology summit. I'll relate some of it to the slides of the talks. (08)
I'll start with Slide 19 in Barry Smith's talk:
> Candidate Upper Level Ontologies
> – Domain Ontology for Linguistic and Cognitive
> Engineering (DOLCE)
> – Suggested Upper Merged Ontology (SUMO)
> – Upper Cyc Ontology
> – Basic Formal Ontology
> – all reflections of recognized need for semantic
> standardization via upper level ontology (09)
That may be true of what the DOLCE, SUMO, and BFO developers say.
But it is definitely *not* true of Cyc. Doug Lenat has explicitly
said that the upper level is the *least* important. He said that
*all* the detailed reasoning is based on axioms and definitions
at the mid level and lower levels. (010)
The most important role of the upper level is to establish a common
set shared terms for types and relations. The top level must be
very underspecified -- usually with little more than type-subtype
and disjoint-from links. The lower level "microtheories" contain
the axioms and definitions needed for detailed reasoning. (011)
Cyc has been developing their ontology for over 28 years (since 1984).
They discovered very early (by 1989) that a single, consistent,
monolithic ontology was unworkable. Instead, they reorganized the
ontology by removing most of the detail from the upper level, and
pushing it down to the possibly *inconsistent* microtheories. (012)
Furthermore, I claim that the same principles are true of BFO, as it is
actually used. Following is an example. (013)
From http://jowl.ontologyonline.org/bfo.html
> Definition: An entity [bfo:Entity] that exists in full at any time in which
> it exists at all, persists through time while maintaining its identity and
> has no temporal parts.
>
> Examples: a heart, a person, the color of a tomato, the mass of a cloud,
> a symphony orchestra, the disposition of blood to coagulate, the lawn and
> atmosphere in front of our building
>
> Synonyms: endurant
> Disjoint With:
> occurrent (014)
For the formal ontology (in OWL), that English definition is a comment
that has no effect on any computation. The relation "Disjoint With"
is the only information that distinguishes the very underspecified
term 'continuant' from the equally underspecified term 'occcurrent'. (015)
But that assumption is inconsistent with the BFO practice. The only
formal constraint is that the subtree under 'continuant is disjoint
from the one under 'occurrent'. The metaphysics stated in English has
no influence on any of the reasoning with or about the BFO ontology. (016)
There are also many questionable points in the examples above. The word
'disposition' raises a huge number of thorny, subtle, and controversial
issues on which professional philosophers have not reached a consensus. (017)
In the slides by Chris Partridge, I very strongly agree with the first
half dozen slides about the need for an architecture based on a "shared
understanding" among the key developers. I disagree with later points: (018)
From Slide 9 by Chris P:
> "Find a scientific man who proposes to get along without any metaphysics...
> and you have found one whose doctrines are thoroughly vitiated by the crude
> and uncriticizedmetaphysics with which they are packed"
> (Charles Peirce, Collected Papers 1.129). (019)
I also quote that point, but I disagree with Chris's assumptions about
the implications:
> In other words, there is going to be a top ontology anyway, Do you want
> to manage it directly (or manage the results of a heterogeneous framework
> on a piecemeal basis)? (020)
I agree that every ontology will inevitably have some kind of top level.
I also agree that it should be managed on a systematic basis. But I
strongly disagree with the following points: (021)
1. The top level should be based on subtle distinctions that even
professional philosophers find controversial. (022)
2. The existing diversity of heterogeneous legacy systems can be
(let alone, *must* be) replaced by rigid philosophical distinctions
that will be imposed upon every conforming application. (023)
Comment by JFS from the thread on the Ontology Summit list,
> The distinctions an ontology requires are determined by its purpose.
> Making distinctions that are irrelevant to the purpose can decrease
> its generality and interoperability. Therefore, the quality of
> an ontology should be measured by its *relevant* distinctions. (024)
Response by Alan Rector,
> Amen... (025)
Following is a revised version of the recommendations that I proposed
in earlier notes to the Ontology Summit list: (026)
1. Avoid subtle and controversial philosophical distinctions in the
top levels of an ontology. (027)
2. Avoid making detailed commitments in the top levels. Push any
complex details or distinctions into the middle and lower levels. (028)
3. Design the ontology in a way that is easy to modify or adapt
as needed -- preferably by automated or semi-automated methods. (029)
Refrigerator principle: When in doubt, throw it out. Any distinction
that is hard to explain to a high-school graduate should be deleted
or pushed down to a specialized microtheory that is designed for
and used by the people who understand that distinction. (030)
John (031)
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