Re: PROV-ISSUE-458: wasInfluencedBy is not irreflexive [prov-dm-constraints]

Hi all,

It would be good to try and reach consensus on this issue.

My response to Tim:

On 23/07/12 13:46, Timothy Lebo wrote:
> Luc, James,
>
> On Jul 20, 2012, at 6:55 AM, James Cheney wrote:
>
>> I added the irreflexivity constraint directly to address concerns raised in discussion by Tim and Tom on issue 454.  I haven't heard whether this proposed fix, or Luc's example of a reflexive communication, addresses their concern.
>>
>> Briefly, I think wasInformedBy(a,a) is a bug,
> +1

I agree the wasDerivedFrom(e,e) where e is an entity is a bug.

I think that
wasInfluencedBy(a,a)
wasInformedBy(a,a)
where a is an activity is plausible:

In a producer/consumer pattern, with a scheduler allocating "tasks to 
perform",  one could imaging an activity
producing a task, and then being the one that consumes it, in the sense
that

wasGeneratedBy(task,a) // a produces the task
used(a,task)  // a consumes and executes the task,



I think the case actedOnBehalfOf is not clear cut either.

actedOnBehalfOf(slave1,uberMaster,a1)
...
actedOnBehalfOf(slaven,uberMaster,an)

where slave 1 . ... n are given responsibility for a1 ... an.

We can imagine that, running out of slave, uberMaster takes direct 
responsibility of activity a_x

actedOnBehalfOf(uberMaster,uberMaster,a_x)

This would  imply  wasInfluencedBy(uberMaster,uberMaster)




>
>
>> and we should fix it by dropping generation-use-communication, and keeping influence irreflexive.  However, I'm not going to fight for irreflexive influence if Luc's example convinces everyone else that it may be reflexive.
>
> 1)
>
> prov-constraints is available to distinguish proper provenance from the scruffy provenance that prov-dm permits.
> A distinguishing characteristic between proper and scruffy is "precision"; The former has it, and the latter need not.
>
> The statement:
>
>        wasInformedBy(a,a)
>
> is hardly precise, and without some precision it is not informative.
> Why would one inform oneself? Didn't the one already know it?
> You're implying two parts of oneself, and should thus distinguish them, describe them separately, and relate them appropriately.

We could probably do that for the entity/agent examples above.
I don't think it works for activity.

Luc

> Meanwhile, it seems like a perfectly reasonable prov-dm statement.

> The same argument applies to the general property wasInfluencedBy.
>
>
> 2)
>
> In a different topic but related to precision, does the latest prov-constraints prevent:
>
> :e prov:wasGeneratedBy :a_1, :a_2 .
> :a_1 owl:differentFrom :a_2 .
>
>
> Thanks,
> Tim
>
>
>
>> I am copying my comments from issue 454 for easy reference:
>>> The irreflexivity constraint was an attempt to address Tim and Tom's concerns, so they should comment on whether your example persuades them that it is not irreflexive.
>>>
>>> My inclination would be that influence and communication should be irreflexive, so this is no problem.
>>>
>>> But if we also allow the generation-use-communication inference, then from the totally reasonable:
>>>
>>> wasGeneratedBy(e,a)
>>> used(a,e)
>>>
>>> we could infer wasInformedBy(a,a) and then wasInfluencedBy(a,a), which would be invalid if influence has to be irreflexive.
>>>
>>> Overall, I think this makes a persuasive argument for dropping generation-use-communication and keeping irreflexivity of influence (and all this entails).
>> --James
>>
>> On Jul 20, 2012, at 9:07 AM, Provenance Working Group Issue Tracker wrote:
>>
>>> PROV-ISSUE-458: wasInfluencedBy is not irreflexive  [prov-dm-constraints]
>>>
>>> http://www.w3.org/2011/prov/track/issues/458
>>>
>>> Raised by: Luc Moreau
>>> On product: prov-dm-constraints
>>>
>>> Going back to the definition in prov-dm,
>>>
>>> Communication is the exchange of some unspecified entity by two activities, one activity using some entity generated by the other.
>>>
>>> I can imagine a service invoking itself (so effectively, exchanging an entity with itself).
>>>
>>> So, it would  be fine to write:
>>>
>>> wasInformedBy(a,a)
>>>
>>> Therefore,
>>>
>>> wasInfluencedBy(a,a)
>>>
>>> which contradicts the constraints:
>>>
>>> http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-constraints.html#impossible-influence-reflexive
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>> -- 
>> 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 Tuesday, 31 July 2012 08:36:32 UTC