When I say context, I like to use the wordnet definition: (02)
"discourse that surrounds a language unit and helps to determine its
Yes - a "river" is always a "river" hence its name. A more accurate
depiction of what I meant to say is that a certain instance might be a
"river" in one context and not in another as you suggest. (04)
>> 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.
> Hmm, context as relative speed: I think that is
> the first time I have come across that particular
> usage. (05)
(DUANE): I suspect that the geo-spatial-temporal relationship is one
context modifier but there would be others. Temperature or granularity
might be another. For example - what is "solid"? To you and I, a sidewalk
is solid. To a neutrino, it is not. Not to worry as I don't know of many
neutrinos who are actively writing ontologies for a human audience but it
does illustrate the importance of the context being somehow present in an
I would presume that the example above is based on an intersection of
multiple contexts. Thinking about how you think is one of the hardest
activities anyone can do (or so I think). (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".
> 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
(DUANE): I think the way I interpreted it, it *could* be a contextual
argument but also might not. Since it is not defined in the example, I
found the example next to useless. (08)
What would have been more accurate is a declaration that "<person_instance>
asserts that <wine_instance> is the best wine". To me, this more accurately
reflects the facts that just stating "<wine_instance> is the best wine". (09)
I was aware of the work that had been done but had not realized there were
active projects. I would like to look into those more. I find the thinking
very interesting. (010)
>> Does it mean that I think it is
>> the best? Is the the author of the ontology?
> Presumably the latter.
>> Has some universally accepted
>> criteria been applied and used to judge it?
>> Without the definition of
>> "best", the example is largely confusing and meaningless IMO.
> 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.
>> There have been some work done around context. Most of it has failed or
>> resulted in an open ended explosion of hypothesis.
> 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
> and some surveys and overviews are available
> (now rather old)
> 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')
>> It is my hope that one day a serious effort will start to really open this
>> topic up.
> 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.
>> 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.
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