Dear Matthew and Pat C, (01)
MW
> You have taken a subtype of physical object and an instance of role,
> so not surprisingly that works. (02)
Yes, indeed. But you can't answer or even discuss any of these issues
precisely unless you have a version of logic in which you can state
them, analyze them, and answer them. (03)
MW
>> The problem with a subtype of both Role and PhysicalObject is that
>> the instances of Role are themselves classes (04)
PC
> That is not the usage in COSMO; if one views an ‘instance’ of a Role
> as a specific whole 4D worm through space-time, then this is actually
> represented in COSMO by a class which is a *subtype* of the generic
> ‘Role’. I think that this has the same effect as your treatment,
> using a different notation. (05)
Talking about 4D worms is an interesting metaphor that might be used
to illustrate some formal analysis. But worms are too slippery to
support precise statements, analysis, and reasoning. (06)
MW
> Please consider expanding "driver" to "Licensed driver".
> ...
> driver and licensed driver are rather different things. If I take driver
> to be the role one takes when actually driving a car, then I am only
> a driver when I am driving. However, I am a licensed driver whether
> or not I am driving, because it is a quite different sort of thing.
> Being a licensed driver is about what one has authority to do, and
> not what one actually does. (07)
You can get the same kinds of examples with natural types. Consider
a bear vs. a Teddy bear. Adjectives in English qualify the noun.
But the question is whether they qualify the individual instances
or whether they qualify the type that is expressed by the noun. (08)
Some adjectives are called "privative" because they deprive the noun
of critical qualities -- for example, fake bear or counterfeit money.
A good test of how an adjective is related to the noun is to paraphrase
the combination "Adj N" as "N that is Adj". For example, (09)
brown bear -> a bear that is brown (010)
Teddy bear -> a bear that is Teddy (011)
fake bear -> a bear that is fake (012)
elderly physicist -> a physicist that is elderly (013)
nuclear physicist -> a physicist that is nuclear (014)
reckless driver -> a driver that is reckless (015)
licensed driver -> a driver that is licensed (016)
For some examples, it makes no sense at all to move the
adjective after the verb 'is', as in 'Teddy' or 'nuclear'. (017)
For some, such as 'brown' or 'elderly', that is possible
and the combination can be translated by a simple conjunction.
Examples include 'brown' and 'elderly'. (018)
For 'Teddy' and 'fake', the sentence is false because no
actual bear can be Teddy or fake. (019)
For others, such as 'reckless' or 'licensed', the meaning
is not necessarily false, but the connection between the
role and the adjective is broken. For example, a driver
who is reckless might be safe as a driver, but reckless
in other aspects of life. (020)
Recommendation: As the metalanguage you need to use a version
of logic that lets you talk about these issues. FOL is good,
but it's even better to use a logic that lets you quantify
over relations as well as instances. (021)
This recommendation does not prevent you from using a restricted
language such as OWL to state your ontology. But you need a more
expressive logic to state and analyze the issues about ontology
and how to define and use it. (022)
John (023)
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