Group of Persons

[nklsbckmnn]

The current definition of Group of Persons reads:

"A Group of Agents that has only Persons as parts."

I would like to propose to change the definition to the following to allow for subgroups of Groups of Persons (the definition of Organization already works like this):

"A Group of Agents that has only Group of Persons or Persons as parts."

or (even better im my opinion, see discussion in the other issue)

"Object Aggregate that has only Group of Persons or Persons as parts."

What do you think?

[swartik]

@eliasweatherfield You are relying on has-part being a transitive property, right? In the version of CCO that conforms to BFO 2.0, has-continuant-part-at-all-times is transitive, but has-continuant-part-at-some-time is not. How would this affect your definition?

[nklsbckmnn]

@swartik Good question.

This problem arises for all continuants with temporary continuant parts (and also those temporarily located_in some continuant), doesn‘t it? (Including Organization)

There are four interpretations of has_part that I can see:

1. Permanent generic. Part does not need to be the same instance at all times. (Some working on RO seem(ed) to find this useful.)
2. Permanent specific/at all times. Part needs to be the same instance at all times. Transitive.
3. Temporary specific/at some time. Not transitive.
4. Temporary specific/at a specific time (e. g. phase). Transitive. (BFO 2020 temporalized)

What is the interpretation of the has_part relation in CCO? My current understanding is this: The interpretation changes from permanent specific/at all times to temporary specific/at a specific time as soon as there is a Stasis of Part Role. Transitivity always holds.

@swartik What do you think about that solution?

@mark-jensen @rorudn Does this sound about right to you?

[nklsbckmnn]

https://www.youtube.com/watch?v=fkkWkTIxrNQ

Barry's slide at 06:37 classifies at-a-specific-time relations as „hidden“ at-all-times relations.

[alanruttenberg]

Regarding permanent generic: It is not representable as a property in OWL. A permanent generic relation would need to be able to handle the following, where x and y are continuants and R is some relation.

• x R y at t1
• not (x R y) at t2
• x R z at t2
• not(x R z) at t1

But there's no place for the "at t" in OWL. But if we drop the time then the above is inconsistent because you have.

• x R y
• not (x R Y)

In other words, there's no way to have a generic relation because there's no time, which means there's no time that something can be different. (x R y) is necessarily specific.

There is a way to express the permanent generic relation using histories, but it's somewhat involved.

It's interesting that some working on RO seem to find this useful. I'm curious how they can think it is useful given that they can't representing it in their OWL. They must be ascribing the usefulness to something different, perhaps unknowingly.

[nklsbckmnn]

Agreed.

[alanruttenberg]

The BFO relation you want is one of the member part relations rather than part. member part is not transitive. None of the offered definitions actually work:

• "A Group of Agents that has only Persons as parts."
• "A Group of Agents that has only Group of Persons or Persons as parts."
• "Object Aggregate that has only Group of Persons or Persons as parts."

These don't work because they rule out the persons having parts, which they do. They are trying to express something like: For the purpose of representing groups of people, the only parts we are interested in are the person parts.

In some cases you can get around this sort of situation by saying something like: the only parts there are are X things or parts of those X things. The problem with that, in this situation, is that it would allow a group of persons to be just the legs, say, of some set of persons.

The last definition is the closest. Changing "as parts" to "as member parts" or just "members" and adding an axiom
has-member-part-at-some-time only 'group of persons' or 'person'

It also has the advantage of removing the term "agent" from the definition, which is superfluous. if "agent" was a good term then all persons would be agents, and so it adds nothing. I don't think it is a good term but will post another issue at some time with my objections to it.

But I'm also concerned with the disconnect between the common understanding of "group of persons" is something like a set of persons, and a set of persons would only have members that are persons. I think defining organization in this way makes perfect sense, but not this term. So if I had my druthers the definition I'd choose is:

Group of persons: an Object Aggregate that has only has Persons as member parts.
with a restriction has-member-part-at-some-time only 'person'

[alanruttenberg]

On reflection I think using agent, given the current definition in common core, is problematic. It would mean that, say, all the patients in a vegetative state in a hospital do not form a group of persons because they aren't capable of performing intentional acts.

[nklsbckmnn]

Thanks for the helpful reply. I agree on the needed relation as well as on your point regarding the desirability of empirical adequacy of the definition.

[nklsbckmnn]

But I'm also concerned with the disconnect between the common understanding of "group of persons" is something like a set of persons, and a set of persons would only have members that are persons. I think defining organization in this way makes perfect sense, but not this term.

I thought some more about this... is the empirical everyday folk "concept" of a group of persons really incompatible with subgrouping?

Let's assume a group of students in a class room is split into two subgroups by the teacher for an exercise. Would we now stop to refer to the group of students in the class room as a "group of persons"? Or would we want to say that the subgroups are not really part of the original group? To me personally, both options prima facie sound odd.

Is a though experiment like this the best way to empirically constrain our definition?

How about this?

Group of Persons =def. An Object Aggregate that has min 2 Persons as member parts and only has (Group of Persons or Persons) as member parts.

The member part relations are transitive, right?

[alanruttenberg]

The member-part relations are not transitive. That's how they are distinguished from part relations.

[nklsbckmnn]

My bad. I have to rethink then.

[nklsbckmnn]

So this is the definition I currently prefer:

Group of Persons =def. An Object Aggregate that only has (Group of Persons or Persons) as member parts.

[nklsbckmnn]

What is the interpretation of the has_part relation in CCO? My current understanding is this: The interpretation changes from permanent specific/at all times to temporary specific/at a specific time as soon as there is a Stasis of Part Role. Transitivity always holds.

I now believe that the correct temporal interpretation is permanent specific/at all times and that this is not changed by the existence of a Stasis.

[alanruttenberg]

@eliasweatherfield group of persons definition is coherent as long as the implications are understood. I think the label isn't quite right but it's only a label. Because of disjointness of members you can't have a person that's a member of some group that's member that's also a direct member. Any member that is a group of persons means that group of persons is an object, by ramge of the member part relation. Finally member part is time indexed so for bfo-2020 you need to decide at-all-time vs at-some-time.

[nklsbckmnn]

@alanruttenberg Thanks for the very helpful reply.

Any member that is a group of persons means that group of persons is an object, by range of the member part relation.

Object wouldn't work though, would it? I just checked BFO-2020 and RO/CCO. The former specifies "material entity" as range, the latter doesn't specify any range. Am I missing something?

Because of disjointness of members you can't have a person that's a member of some group that's member that's also a direct member.

I saw this in the BFO-2020 definition (but not in the RO/CCO definition). It is definitely a big problem for my use case. Do you have any objections against having a variant of the relation without disjointness?

Finally member part is time indexed so for bfo-2020 you need to decide at-all-time vs at-some-time.

I agree with you that at-some-time is needed here.