John F. Sowa wrote:
> Dear Matthew, David, Chris, Pat, John,
> MW> So Matthew West the employee of Shell is only the same
> > thing as Matthew West the person if Matthew West is an
> > employee of Shell for the whole of his life.
> Nonetheless, it is always true in both 3-D and 4-D models
> that every instant of time when MW is an employee, MW is
> also a person. Therefore, Employee < Person.
> MW> The employee instance is not a person-for-the-whole-of-their-life,
> Of course. But every employee instance is a part of the person
> instance. That is exactly what is implied by Employee < Person.
> DD> Simply said, identifying whether something is a 'natural kind'
> > or a role might be very hard in some cases and completely depends
> > on the level of granularity of your ontology or the background
> > of the modeler.
> This is one of many reasons why trying to draw a hard-and-fast
> distinction that holds for every possible case is not easy.
> Therefore, it makes more sense to put all the concept types into
> a single hierarchy and leave it underspecified, if necessary.
> CP> Your notion of employee does not distinguish between employers
> > - and it is also temporalised - one is an employee at a time.
> No. The statement X<Y is about *types*, not about *individuals*,
> and the *definition* of a type is independent of space and time.
> What is time dependent is whether a particular individual is
> an instance of a particular type at a given time.
> CP> It seems that implicitly mean that *at time t1*, X < Y means
> > that every instance of X is an instance of Y. Maybe better to
> > say that X <t1 Y means that at t1 every instance of X is
> > an instance of Y.
> No. To say Employee<Person means that at *every* point in time
> and place, if x is an employee, then x is a person. It doesn't
> matter whether x is an employee of more than one company at
> that time, the simple statement "x is a person" is still true.
> CP> I am not sure how this would deal with employees with
> > multiple employers at the same time. It looks as if it
> > would have problems. Could you explain.
> Please remember that Employee < Role. Therefore, one cannot
> be an employee without being in a role. If you are in the
> same type of role with two different companies, then you
> are playing two roles at the same time. You have not become
> two different individuals.
> CP> However, this is not the notion I find when I look at
> > systems. Typically a system will say who the person is
> > employed by, when he/she started employment, and if
> > appropriate when they left employment.
> Of course. And during the entire time, that person did
> not cease being a person.
> CP> a bishop would be a sub-type of person. If James were
> > a bishop, you would say that there is only one James who
> > is both a person and a bishop (at time t1).
> Of course.
> CP> If one left ones property to the Bishop, then when James
> > dies in office, the property would remain the property of
> > the bishop and not pass to James's heirs.
> That depends on how you stated the deed, either explicitly
> or implicitly. There are usually legalistic phrases attached,
> such as "ex officio", to indicate how the money is given.
> If a clerk at McDonald's gives you a hamburger and asks for
> payment, the money is implicitly designated for McDonald's,
> not the clerk. But if the clerk happens to be your niece, you
> can give her a gift for her birthday while you're buying the
> burger, and it won't go into the money drawer. But there is
> still only one person there -- not a separate clerk and niece.
> PH> Seems to me pretty obvious that I am a person and I am also
> > an employee, and also that there is just one of me.
> I'm glad that we're on the same side in this debate.
> JFS>> If I'm assigned a task as an employee, it's my task, not
> >> the task of some virtual employee.
> JB> Evidently not as settled after all: this is the qua-individual
> > debate, which is alive and well last I heard.
> But note the "qua" -- that is a sign that we're not talking about
> the number of individuals, but about the number of different
> roles that a single individual may be playing at the same time.
> JB> The usual counter-discussions to the above point are the legal
> > ones I think: who is responsible and who can get sued for what?
> > Or the passengers-on-Airline-X examples: how do you count them?
> > And what have you counted once you have counted them? Seems like
> > there are lots of virtual artefacts waiting to take their place
> > in the discussion...
> But those "artefacts" are multiplicities of roles, not of
> individuals. There is no problem about counting the number of
> people on the plane. But when a plane has multiple flight numbers,
> it can be hard to determine which passenger-role any particular
> individual is playing at that moment.
> JFS>> Subtype has a very clear and simple definition: X < Y
> >> means that every instance of X is an instance of Y.
> PH> I would prefer to say that it implies this, but subtype
> > is actually somewhat stronger.
> Sorry, I should have said "implies" rather than "means". It's
> a one-way implication, not an "iff".
> JFS>> It implies that the entire spatiotemporal extent of Employee
> >> is included in the spatiotemporal extent of Person.
> PH> Not unless you conflate class membership with temporal parthood.
> > I think Matthew is keeping these ideas separate.
> This may be the crux of the distinction. Pat and Matthew are equating
> types with classes (which I would interpret as extensional set-like
> things). But I interpret types as intensional, name-like things.
> Therefore, I interpret X<Y as implying that for every space-time point
> where the type label X is appropriate, the type label Y is appropriate.
> FP>> In one of the extensions of DOLCE, a role is
> >> considered a non-physical social object.
> PH> I think that is a rather special interpretation of 'role'.
> > It had better be, as the idea of 'social object' makes no sense
> > at all in many domains of application.
> As an example, consider the definition of "planet" vs. "satellite".
> There are some satellites in the solar system that are larger than
> the planet Mercury. To use my criterion, you can't tell whether
> they are planets or satellites just by looking at them in isolation.
> Therefore, the distinction must be by their role in relation to
> other bodies in the solar system. But there is an objective test
> for making the distinction.
> PH> Everyday common sense is simply one more area of expert
> > specialization, like protein folding or cell biology: we don't
> > think of it that way only because all competent adults are
> > experts, like chess grandmasters in this particular domain.
> > But it is just as peculiar and idiosyncratic as any other,
> > and ontologies designed for it don't automatically transfer
> > to other domains.
> I agree. One generation's cutting-edge research is the next
> generation's common sense -- for example, computer technology.
> FP>> If a certain entity which was previously identified as
> >> chair, is never used again for sitting but only for, say,
> >> a step for changing light bulbs, it stops playing the role
> >> of being a chair and is hence only playing the role of
> >> a step for changing light bulbs (?).
> PH> It would still be a chair, however (or at least one could
> > reasonably claim this.) We would refer to it that way, and
> > it would be listed that way in a product catalog.
> Yes, there is a characteristic shape for a chair. Fragile
> antiques in a museum are chairs even though nobody is allowed
> to sit on them.
This is a good example. The physical object that used to play the role
of a chair in 1632 now plays the role of a historical artifact. Since
roles can be seen as social objects, one can assign and withdraw roles.
It is possible to take this physical object (which has certain direct
qualities like mass, volume, color and shape (e.g. four-leged)) out of
the museum, sell it at Sotherby's and the buyer might assign the role of
being a chair to it again and use it for sitting.
I do not seriously claim that chairs are roles. Yet I am struggling
finding it difficult to work with roles while not letting them take over
the whole ontology. How to "balance" the usage of roles in ontology
I am somehow reminded at the taxonomy for species. The taxonomy that was
valid for quiet a long time in biology and payed at lot attention to the
animals we can easily observe (larger plants and mammals), thus making
them central in the taxonomy. With the newer findings in biology, this
taxonomy can be challenged. The result is that most species are bacteria
and other "small bugs". If such a new taxonomy is depicted in a graph,
it does not look nice and the things (animals and plants) we are used to
perceive and interact, are pushed to a tiny little branch which seems
not to reflect the importance that one might like to give them.
Might it be possible, that the things we physically interact with (the
entities we call in natural language chair, table, cup and person) get
way to much attention in our taxonomies and that the branch of roles is
neglected, since it is difficult to deal with and make an ontology look
very unbalanced? (01)
Ontologically there might be a benefit in the possibility to
disambiguate the qualities one assigns to an entity. (I am talking about
A certain human might have the qualities height (1,8m), mass (75kg) ...
while the employee (that is played by that human) has the qualities
efficiency (medium), loyalty (high), humor (high) ...
while the father (that is played by that human) has the qualities
patients (enormous), humor (low) (02)
In natural language, it would be the normal way to refer to the human,
the employee and the father with, say, "Tom". The same NAME trefers to
different entities. Here is, in my understanding, where semantic
heterogeneity is introduced. There are three different meanings to the
label "Tom". Tom can be funny at work and not so funny at home. If it
would be possible to clearly identify the entity which is bearing the
humor-quality, ambiguity that emerges from "Tom" being assigned to three
different entities could be resolved.
(The role entities are specifically dependent on the entity which plays
them. They exist only as long as their bearer exists.) (03)
Finding ways to (05)
> PH> I actually prefer to have a clear-cut abstract/spatiotemporal
> > distinction and firmly relegate all mathematically described
> > collections to the former category. Its just easier to remember,
> > basically.
> There's a lot to be said for definitions that are easy to remember
> and minimize confusion. Whitehead used the term "eternal entity"
> for anything that does not have spatiotemporal coordinates, but
> it led people to think he was talking about heaven and angels.
> I'm happy with the abstract/spatiotemporal distinction, and I
> would put all mathematical structures into the abstract category.
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