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Re: [ontolog-forum] Role of definitions (Remember the poor human)

To: Duane Nickull <dnickull@xxxxxxxxx>
Cc: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Wed, 14 Feb 2007 16:54:17 -0600
Message-id: <p0623090cc1f93de2d781@[]>
>I have been toying with these problems ever since I got introduced into the
>ontologists world.  One thing that bothers me with a lot of ontology work is
>the lack of a context modifier concept.  Context is such an important
>aspects of cognitive behavior and semantics in general.    (01)

The trouble with this observation is that the 
meaning of the word "context" is so elastic that 
the claim is close to vacuous. I have attended 
"context" workshops in which every single paper 
presented assumed a different notion of 
"context". Of course, one can view this situation 
as itself an illustration of your point, but it 
may also help to explain why technical progress 
in this area tends to be rather erratic.    (02)

Can you, er, define what you mean by "context" ?    (03)

>  A tree is not
>always a tree, a river is not always a river.    (04)

I see what you mean, but unfortunately this way 
of putting it illustrates some of the problems. 
As a matter of fact, a river IS always a river: 
this is a necessary truth. What you mean is, I 
suspect, an actual river can be treated as 
something else for certain purposes, something 
which likely shares some properties with rivers 
but not all of them. True. Now one has to ask, is 
an ontology supposed to reflect the reality or 
the contextual 'view' of the reality?    (05)

>  A glass of water sitting on a
>desk in front of you will not be elevated in your own tuple stores yet a
>glass of water approaching your windshield at 60MPH will based on your
>perception that it is a threat to your safety.  They are the same object but
>in different contexts have different meaning.    (06)

Hmm, context as relative speed: I think that is 
the first time I have come across that particular 
usage.    (07)

>Even the basic examples that used to come with Protégé were flawed IMO.  The
>wine example was screaming for the aspect of context to be included in the
>ontology given the concept of "best wine" is contextually dependent upon
>your definition and criteria for "best".    (08)

It is dependent on your concept of "best", yes. 
Put another way, it uses the term in a very 
under-determined way. Why do you say this is 
"contextual", though? What has this situation got 
to do with contexts, and in what sense of 
"context"?    (09)

>  Does it mean that I think it is
>the best?  Is the the author of the ontology?    (010)

Presumably the latter.    (011)

>  Has some universally accepted
>criteria been applied and used to judge it?    (012)

No.    (013)

>  Without the definition of
>"best", the example is largely confusing and meaningless IMO.    (014)

It does not mean very much, but it is not 
meaningLESS. It has whatever meaning can be 
gleaned from the axioms in the ontology. The same 
is true for all concept names in any ontology.    (015)

>There have been some work done around context.  Most of it has failed or
>resulted in an open ended explosion of hypothesis.    (016)

Well, quite a lot of reasonably serious work has 
been done without utter failure, though of course 
not entirely without controversy. There has been 
a series of quite technical workshops, for example    (017)

http://www.nexus.uni-stuttgart.de/COMOREA/2006/CallForPapers06_files/comorea06-cfp.pdf    (018)

and some surveys and overviews are available    (019)

(now rather old)
http://www.cs.bilkent.edu.tr/~akman/book-chapters/mcgraw/mcgraw2002.doc    (020)

and I belive there is a journal devoted to the 
topic. John McCarthy was the first to suggest a 
contextual logic, and it has since been quite 
sharply formalized by others and has given rise 
to a lot of work, including many applications and 
implementations of context-reasoning engines (Try 
googling "context logic"). Cyc, probably the 
largest integrated ontology ever built, has been 
based firmly on context logic for a decade or so, 
and uses it centrally (their preferred term is 
'microtheory' rather than 'context')    (021)

>It is my hope that one day a serious effort will start to really open this
>topic up.    (022)

Im not sure what you regard as serious, but you 
might cast an eye over some of the literature. By 
the way, our logic IKL was developed in order to 
provide for a way of handling contexts in full 
generality but which does not require using a 
context *logic*. I can expand on this point if 
you are interested.    (023)

Pat    (024)

>On 2/14/07 9:41 AM, "John F. Sowa" <sowa@xxxxxxxxxxx> wrote:
>>  Pat, Chris, Kathy, and Barry,
>>  The problem of stating necessary and sufficient conditions
>>  for defining anything is nontrivial, even in mathematics.
>>  For phenomena in nature or the results of typical human
>>  behavior, definitive statements are problematical, to say
>>  the least.
>>  Belief revision systems, database systems, and knowledge-based
>>  systems distinguish levels of "entrenchment" (whether or not
>>  they use that term), and I believe that an ontology should also
>>  make such distinctions at the metalevel.  Following are some
>>  "levels of entrenchment" in descending order of strength:
>>    1. Type hierarchy.  The classical tree or partial ordering
>>       introduced by Aristotle and first drawn by (or attributed
>>       to) Porphyry.  It's useful in every field, it's not going
>>       away, and we should recognize it as the minimal requirement
>>       for an ontology.
>>    2. Necessary distinctions.  The differentiae that split any
>>       type into two or more subtypes.  If the split is binary
>>       (A or not-A), then it is both necessary and sufficient for
>>       distinguishing the two subtypes from one another, but the
>>       conditions for characterizing the supertype might not be
>>       necessary and sufficient.
>>    3. Constraints.  Additional statements that characterize the
>>       types or the interactions of entities of various types.
>>       The constraints are necessary relative to the ordinary
>>       facts in level #4, but they might not be considered
>>       defining characteristics.
>>    4. Ordinary facts.  Ground-level assertions that must be
>>       consistent with statements at the above levels, but they
>>       may violate defaults at level 5.
>>    5. Defaults and probabilities.  Statements that are usually
>>       true of entities of a given type or types, but they are
>>       at the bottom of the entrenchment pole.  A probable
>>       statement is a default with an associated value that
>>       indicates its likelihood or frequency of occurrence,
>>       given the occurrence of some other condition.
>>  Systems of entrenchment levels along such lines are widely
>>  used and should be supported.  Cyc, for example, has 3 levels:
>>  True, true by default, unknown (and the negations -- false
>>  by default and false).  But I think that Lenat would agree
>>  that a privileged level should be added for some of the
>>  axioms, especially ones that define the type hierarchy.
>>  A declaration of which level a particular statement belongs to
>>  would not be part of the first-order theory, but it would be
>>  a metalevel statement that should definitely be considered
>>  part of the ontology.
>>  John
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