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Re: PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually "IVP of" each other [Conceptual Model]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Mon, 02 Apr 2012 10:27:58 +0100
Message-ID: <EMEW3|b102f0ef729fc9225d1adea679211779o31AS108L.Moreau|ecs.soton.ac.uk|4F79711E.3050000@ecs.soton.ac.uk>
To: James Cheney <jcheney@inf.ed.ac.uk>
CC: Paul Groth <p.t.groth@vu.nl>, "public-prov-wg@w3.org" <public-prov-wg@w3.org>
Hi James,

I am not trying to defend one point of view or the other, but I seek 
some guidance
about what to write in part II, which should be released by end of the day.

/Taking my editor's hat off: *my* view is that we should not specify any 
of these properties
in our documents, and we should see what the community does with the 
relations.
/
Editor's hat on, further comments below:


On 04/02/2012 09:58 AM, James Cheney wrote:
> Hi Luc,
>
> The point of having each Entity mapped to a (unique) Thing in the 
> semantics is to avoid this kind of confusion.
>
> I did it this way precisely because of examples like this, and because 
> of I thought there was a rough consensus that specialization
>
... that specialization ...?? is transitive you mean?


> If you think the formal semantics as is mismatches the data 
> model/constraints and should not do this, please raise an issue on it 
> and we can discuss it.

I have no view about it. The english definition does not disallow for my 
interpretation.  So, something
needs to be changed somewhere.

My reading of Jim and Stian's messages is that transitivity does not 
hold, but apologies if I have misread.

>
> Considering your (brief) example (I think I am restating Stian's 
> response in more formal terms):
>
> So there are two things:
>
> thing1 = woman in red
> thing2 = man in black
>
> I'll assume their lifetimes both include t1,t2.  From t0 to t1, thing1 
> is in the chair, then thing1 leaves and thing2 gets in the chair at t2.
>
> If you have one "entity"
>
> ent0 = person on chair at times [t1,t2]
>
> then there can't be a single thing that the entity maps to, i.e., it's 
> not allowed in the semantics.

is it the consensus?
how do we modify the english definition to reflect this?
>
> You need two entities
>
> ent1 = person on chair at time t1
> ent2 = person on chair at time t2
>
> Note that officially, we are not required to give ent1 and ent2 
> different attributes (or any attributes at all), but if we intend them 
> to denote different things
>
> Incidentally, the example you gave has nothing at all to do with 
> specialization: specialization is a relation on entities, not things, 
> and the two entities ent1 and ent2 are not specializations of each 
> other, nor is ent1 or ent2 a specialization of ent0 (or vice versa). 
>  Ent0 is not even a sensible entity anyway.  So, in my view your 
> example is not a use case for allowing entities to refer to multiple 
> things.

I am not sure which example you refer to.
But surely, thing1 and thing2 can also be regarded as entities!

>
> I see absolutely no point to or motivation for allowing an entity to 
> refer to more than (or less than) one thing.
>
So, still trying to understand, if it's the case, what is the point of 
talking about things?
Shouldn't the English definition of these concepts be expressed without 
the term 'thing'?

Luc


> --James
>
> On Apr 1, 2012, at 8:20 PM, Luc Moreau wrote:
>
>>
>>
>>
>> On 1 Apr 2012, at 12:12, "Paul Groth" <p.t.groth@vu.nl 
>> <mailto:p.t.groth@vu.nl>> wrote:
>>
>>> My answers:
>>>
>>> 1. An entity refers to one thing that thing may or may not be identified
>>
>>
>> At a given point in time, possibly, but is it the case when time changes?
>>
>> Can't recall the exact detail, but the 'customer on the third chair' 
>> may be the
>> woman in red at t1 and the man in black at t2. Can't it?
>>
>>
>> Luc
>>
>>
>>>
>>> 2. Specialization thus is defined in terms of 1
>>>
>>> Paul - not a specialization/alternator guru
>>>
>>> On Apr 1, 2012, at 9:46, Luc Moreau <l.moreau@ecs.soton.ac.uk 
>>> <mailto:l.moreau@ecs.soton.ac.uk>> wrote:
>>>
>>>> Hi all specializationOf/alternateOf gurus,
>>>>
>>>> The current definition of alternateOf does not allow us to decide 
>>>> whether James's or my interpretation
>>>> is right.  The question is essentially: does an entity refer to one 
>>>> and only one thing or not.
>>>>
>>>> So,
>>>>
>>>> 1. What is intended?
>>>> 2. How do we clarify definitions?
>>>>
>>>> Cheers,
>>>> Luc
>>>>
>>>>
>>>> On 31/03/2012 15:46, James Cheney wrote:
>>>>> On 30/03/12 10:01, Luc Moreau wrote:
>>>>>>
>>>>>> Dear all,
>>>>>>
>>>>>> I am getting conflicting messages on this topic!
>>>>>>
>>>>>> James has listed some properties derived from the semantics
>>>>>> http://lists.w3.org/Archives/Public/public-prov-wg/2012Mar/0470.html
>>>>>> But not all of them seem to be aligned with what we are reading 
>>>>>> on this thread.
>>>>>>
>>>>>> So, I started drafting a section in prov-dm part II listing the 
>>>>>> properties of these relations [1].
>>>>>>
>>>>>> I am proposing to justify each property either by reasoning based 
>>>>>> on its definition,
>>>>>> or by a counter-example.
>>>>>>
>>>>>> *Your suggestions are needed to help us complete this section. *
>>>>>>
>>>>>> James, unless my reasoning is incorrect, I do not have 
>>>>>> transitivity for specializationOf.
>>>>>
>>>>> Hi Luc,
>>>>>
>>>>> Your reasoning (quoting from [1])  is:
>>>>>
>>>>>> Specialization is /not transitive/. Indeed if 
>>>>>> specializationOf(e1,e2) holds, then there is some common thing, 
>>>>>> say e1-2 they both refer to. Likewise, if specializationOf(e2,e3) 
>>>>>> holds, then there is some common thing, say e2-3 they both refer 
>>>>>> to. It does not follow there is a common thing both e1 and e3 
>>>>>> refer to.
>>>>>
>>>>> In the WD3 formal semantics [2], I modeled 
>>>>> entities-referring-to-things as a function thingOf : Entity -> Thing.
>>>>>
>>>>> Thus, if thingOf(e1) = e1-2 = thingOf(e2) and thingOf(e2) = e2-3 = 
>>>>> thingOf(e3) then (by transitivity of equality) e1-2 = e2-3 and all 
>>>>> three entities refer to the same thing, e1-2.
>>>>>
>>>>> Of course, it is an assumption I made that an entity "refers to" 
>>>>> exactly one thing.  If we want to allow entities to refer to 
>>>>> multiple things, then the reasoning I give above fails, and 
>>>>> specializationOf is not necessarily transitive.
>>>>>
>>>>> --James
>>>>>
>>>>> [1] 
>>>>> http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-dm-constraints.html#component4
>>>>> [2] http://www.w3.org/2011/prov/wiki/FormalSemanticsWD3
>>>>>
>>>>>
>>>>> The University of Edinburgh is a charitable body, registered in
>>>>> Scotland, with registration number SC005336.
>>>>>    
>
>
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>    

-- 
Professor Luc Moreau
Electronics and Computer Science   tel:   +44 23 8059 4487
University of Southampton          fax:   +44 23 8059 2865
Southampton SO17 1BJ               email: l.moreau@ecs.soton.ac.uk
United Kingdom                     http://www.ecs.soton.ac.uk/~lavm
Received on Monday, 2 April 2012 09:28:46 GMT

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