Folks, (01)
To begin to address the "typing" of ontology that the Ontology Summit
prospectively would like to address, I'm beginning this new thread. I'd
suggest using the subject line to clearly distinguish any NEW topic, so
that skimmers/samplers/surfers can focus more meaningfully. Why?
Because we really don't yet have metadata-annotated or "semantically"
threaded email -- except for subject lines. For example, currently we
have the topic "ontology as logical theory?". (02)
I'm bringing forward my suggestion (message dated Thursday, January 25,
2007 2:14 PM, under the Subject = Re: [ontology-summit] Defining
"ontology"), simply as a strawman, slightly enhanced with a canonical
dimension/feature name (e.g., Formality) and a scale of values (e.g.,
Informal=0, Formal=1). I don't know if this will prove useful, but let
us know your thoughts. Note that these are not pejorative: the feature
name and the values are relatively arbitrarily chosen (though I have my
own biases). (03)
Please comment on/modify/trash these. Note if you strongly believe in
one definition or think this effort is not worthwhile or the dimensions
are mischaracterized, please let us all know. (04)
Dimensions of Ontology Types: (05)
1) Formality: Informal (Formality = 0) vs. Formal (Formality = 1)
2) Expressivity: Expressivity of the semantic model (i.e., underlying
knowledge
representation language or logic) [No scale determined yet]
3) Concept-based: Term (Concept-based = 0) vs. concept (real world
referent)(Concept-based = 1)
4) Mathematical Ordering: Mathematical ordering, structure, definition
of the privileged
parent-child relation: [No scale determined yet]
5) Application focus/use cases, etc. (part of this is precision of the
service needed, e.g., metadata/topic terms for a document to aid in
broad doc topic retrieval vs. a semantic service query, specfication,
or composition): [No scale determined yet]
6) Granularity (precision, scope): [No scale determined yet]
7) Development Philosophy: Empirical (bottom-up) [0] vs. Rationalist
(top-down) development [1]
methodology (i.e., arbitrary folks add or annotate terms/concepts vs. a
rigorous ontology development) [No scale determined yet; Some
combination? Middle-out? But what does that mean?]
8) Human-Coded: Human-coded [1] vs. machine-learned/generated [0]
9) Automated reasoning (and complexity of that, i.e., one could have
transitive closure or subsumption down a subclass graph vs.
theorem-proving): [No scale determined yet]
10) Descriptive vs. prescriptive (i.e., a commonsense or
conceptually-profligate ontology vs. an ontology that specifies that
this is the way the world is): [No scale determined yet]
... (06)
Other criteria perhaps address properties of the content, i.e., Average
density/bushiness: [Probably a real scale, once we define density,
bushiness], etc. (07)
Some notes:
1. Expressivity, Mathematical Ordering, and Automated Reasoning are
probably related.
2. Application focus/use cases: this is still nearly arbitrary, but I
would like us to think about recall/precision of the application/use
case as perhaps a better scale or paired scales, i.e., [Recall = 0,
Precision = 0] vs. [Recall = 1, Precision = 1], but then we need to
define Recall and Precision. Or there may be some normalized score that
factors both Recall and Precision into a composite real number. Then
again, a better dimension may be application complexity if that can be
agreed on, i.e., Constant, Linear, Logorithmic, Exponential, ...
NP-Complete, ... Of course, if we go with this latter notion, then it
is probably closely related to (1) above, i.e., if a problem is
characterizable as NP-Complete, then there is probably a corresponding
expressivity model requirement. This gets into expressive complexity,
i.e., the correlation between the expressiveness of the language and
complexity of the computation. (08)
Thanks,
Leo
_____________________________________________
Dr. Leo Obrst The MITRE Corporation, Information Semantics
lobrst@xxxxxxxxx Center for Innovative Computing & Informatics
Voice: 703-983-6770 7515 Colshire Drive, M/S H305
Fax: 703-983-1379 McLean, VA 22102-7508, USA (09)
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