Re: PROV-ISSUE-467 (activity-start-req-trigger): Do activity start/end always require trigger? [prov-dm-constraints]

I've given this a thought over night, I think that for the purpose of
LC, we can close this issue, if we just do a strawman poll in today's
meeting over whether it is OK to require activity start/end to have
triggers. (which I would vote 0 for)


On Wed, Aug 8, 2012 at 10:54 AM, Stian Soiland-Reyes
<soiland-reyes@cs.manchester.ac.uk> wrote:
> On Wed, Aug 8, 2012 at 9:51 AM, Luc Moreau <l.moreau@ecs.soton.ac.uk> wrote:
>
>> Can you explain what you mean by activities that just 'are'?
>> Do you mean they have no cause? Or don't know the cause?
>
> An activity in PROV might be a description of an observed process,
> rather than a record of a pre-planned activity which is already
> understood.  What I interpret as a process depend on my assumptions of
> what constitutes the system, etc. So if I observe that a flock of
> birds start flying together as a single swarm, I can say that
> swarmFlying started at 11:58 and ended at 12:04.
>
> However, swarm flying is not 'caused' by anything, it is just an
> observed pattern where we see multiple birds moving in unison. Forcing
> this to have triggers means we have to invent trigger entities like
> "coherentProximitiesBetweenBirds" and "avoidanceRules" which we then
> need to explain the origin of. But any provenance trace is limited by
> its selected boundaries of assumptions, observations and view of the
> world; hence there would be statements which we don't make, which
> would go 'beyond' the chosen scope. For instance in the provenance for
> the Olympics world records, we might not include the position of the
> moon, although it would have affected the particular tide level in the
> river during the rowing event.
>
> Similarly, a shop keeper might see 10 customers in a row buy the same
> chocolate. What triggered this :chocolateBuying activity? Was there a
> commercial for this chocolate? Did the shop put up a nice poster? We
> humans are insisting on finding justifications for everything, but
> sometimes it might just be random behaviour - this particular day, 10
> people, choosing independently for different reasons, just happened to
> all chose the same chocolate. So your activity is 'triggered' by your
> own definition of it.
>
> (I know this is dangerous waters, because this argument applies to
> entities as well; it might just be the observers particular
> characterisation that 'forms' a particular entity, and no activity for
> wasGeneratedBy can be found).
>
>
>> I am concerned about suddenly making triggers non-expandable
>> (i.e. not replaceable by existential variables) because we don't know
>> the implications of that change.
>
> I understand that.  I am not giving a blank -1 to requiring triggers,
> but I wonder if the WG has agreed on them being required to exist
> (although they might not be stated). If we find another solution to my
> infinite loop, I can reluctantly let them stay, although I  must admit
> I find them quite artificial in some circumstances.
>
>
> It is a worry that as we moved 'all the difficult bits' from PROV-DM
> into PROV-Constraints, many of the issues that earlier caused heated
> discussion has been silenced away, to be decided by two editors in
> private discussions. I am not trying to reheat those kind of
> discussions, but I am just concerned if those have been cut short
> rather than been settled and agreed.
>
> --
> Stian Soiland-Reyes, myGrid team
> School of Computer Science
> The University of Manchester



-- 
Stian Soiland-Reyes, myGrid team
School of Computer Science
The University of Manchester

Received on Thursday, 9 August 2012 09:56:28 UTC