RE: PROV-ISSUE-67 (single-execution): Why is there a difference in what is represented by one vs multiple executions? [Conceptual Model]

Luc,

If we cannot tell if PEs are atomic, isDerivedFrom and
isDerivedFromInMultipleSteps would appear to be synonyms - one can't
make one transitive and the other not if you have no guarantee that what
was reported as one PE for isDerivedFrom cannot be multiple PEs.
Transitivity should not be a function of how the witness reports the PE.

Said differently, I think the discussion about multiple steps is an
attempt to get back to the fact that derivedFrom could be defined two
ways if we don't know about the nature of a PE -  one that is trivial
based on the used/generated relationships, which would be transitive,
and one that is only assertable, which can only be transitive iff PEs
are atomic and Bobs are atomic.  (So really we need
isDerivedFromInMultipleStepsAndOrFromAggregateObjects()). The latter is
really trying to get at the idea that something in the output came
directly from the input, e.g. some physical material has been
incorporated.

I think it would be useful to know if the group thinks we need both. If
so, I would suggest having names for them that don't involve discussion
of multi-step or aggregate Bobs if we don't want to define atomicity.
Maybe inheritsFrom (assertable) and derivedFrom(transitive)?
IncorporatedFrom()?

 Jim

> -----Original Message-----
> From: public-prov-wg-request@w3.org [mailto:public-prov-wg-
> request@w3.org] On Behalf Of Luc Moreau
> Sent: Monday, August 01, 2011 11:28 AM
> To: public-prov-wg@w3.org
> Subject: Re: PROV-ISSUE-67 (single-execution): Why is there a
difference in
> what is represented by one vs multiple executions? [Conceptual Model]
> 
> Hi Jim,
> 
> The text does not mention atomic processes, and there was (in my mind)
no
> intent of having them in the model.
> As I asked Simon, could you explain with an example in the context of
the
> document
>   what the problem is.
> 
> Thanks,
> Luc
> 
> 
> 
> On 01/08/11 15:31, Myers, Jim wrote:
> > +1 - there are very few 'atomic' processes that could not be
described as an
> aggregate graph of other processes. Given that we don't know anything
in PIL
> about the nature of processes, it seems like distinguishing direct
versus
> multiple will not be a clear binary split and we'd essentially end up
treating
> both the same way.
> >
> >   Jim
> >
> >
> >> -----Original Message-----
> >> From: public-prov-wg-request@w3.org [mailto:public-prov-wg-
> >> request@w3.org] On Behalf Of Simon Miles
> >> Sent: Monday, August 01, 2011 7:03 AM
> >> To: Provenance Working Group WG
> >> Subject: Re: PROV-ISSUE-67 (single-execution): Why is there a
> >> difference in what is represented by one vs multiple executions?
> >> [Conceptual Model]
> >>
> >> Hi Luc,
> >>
> >> I follow your argument, but it seems tangential to my point. The
> >> following argument still seems inevitably true to me:
> >>
> >> Activity in the world that uses one BOB and generates another *can*
> >> be described in PIL as multiple process executions or a single
> >> process execution (regardless of whether it actually is described
in
> >> these different ways or not, or whether accounts are required or
not).
> >>
> >> Therefore, what one process execution denotes is not distinct from
> >> what multiple process executions denotes, we have just provided
more
> >> detail in the latter description (and this detail is, in any case,
> >> removed when saying "is derived from").
> >>
> >> Therefore, isDerivedFrom and isDerivedFromInMultipleSteps as
defined
> >> do not describe anything different in the world, so we have two
terms
> >> for representing the same thing.
> >>
> >> I know that we've debated this or similar before, but it is still
not
> >> clear to me where the fault lies in my argument, or what
> >> isDerivedFromInMultipleSteps really represents. If it's only me
> >> that's confused, I understand there are more urgent concerns
(though
> >> I'd still like to understand).
> >>
> >> Thanks,
> >> Simon
> >>
> >> On 1 August 2011 09:25, Luc Moreau<L.Moreau@ecs.soton.ac.uk>
> wrote:
> >>
> >>> Hi Simon,
> >>>
> >>> If I understand you correctly, you are suggesting that the
following
> >>> two assertions hold together.
> >>>
> >>> isGeneratedBy(e5,pe5,out)
> >>> isGeneratedBy(e5,pe4,out)
> >>>
> >>> But this is not legal, since it is stated that one BOB is
generated
> >>> by at most one process execution.
> >>>
> >>> What you are suggesting should be encoded in a separate account
> >>> (though we have not defined this yet!).
> >>> A one-step derivation then expands to one process execution in a
> >>> given account.
> >>> In a separate account, there may be a multi-step derivation
between
> >>> the same two BOBs and it would expand into multiple process
> >>> executions.
> >>>
> >>> Does it make sense?
> >>> Regards,
> >>>
> >>> Luc
> >>>
> >>>
> >>> On 07/29/2011 05:52 PM, Provenance Working Group Issue Tracker
> wrote:
> >>>
> >>>> PROV-ISSUE-67 (single-execution): Why is there a difference in
what
> >>>> is represented by one vs multiple executions? [Conceptual Model]
> >>>>
> >>>> http://www.w3.org/2011/prov/track/issues/67
> >>>>
> >>>> Raised by: Simon Miles
> >>>> On product: Conceptual Model
> >>>>
> >>>> By the definition, "a process execution represents an
identifiable
> >>>>
> >> activity". This does not seem to preclude one process execution
> >> assertion denoting, at a coarse granularity, the same events in the
> >> world denoted by multiple process executions in other assertions.
> >>
> >>>> If so, then in the File Scenario example, I could add a
> >>>> coarse-grained
> >>>>
> >> process execution representing the whole e1-to-e5 activity:
> >>
> >>>>     processExecution(pe5,collaboratively-edit,t)
> >>>>     uses(pe5,e1,in)
> >>>>     isGeneratedBy(e5,pe5,out)
> >>>>
> >>>> But then Section 5.5.2 distinguishes between "a single process
> execution"
> >>>>
> >> and "one or more process executions". Following the argument above,
> >> these could represent exactly the same occurrences in the world.
> >>
> >>>> So there is no difference between what is denoted by one and
> >>>> multiple
> >>>>
> >> process executions, and so no difference between isDerivedFrom and
> >> isDerivedFromInMultipleSteps as described. Whether e5 was derived
> >> from
> >> e1 appears to me to be entirely independent of how many process
> >> executions were involved.
> >>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>> --
> >>> 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
> >>>
> >>>
> >>>
> >>>
> >>>
> >>
> ____________________________________________________________
> __
> >> ________
> >>
> >>> This email has been scanned by the MessageLabs Email Security
System.
> >>> For more information please visit http://www.messagelabs.com/email
> >>>
> >>>
> >>
> ____________________________________________________________
> __
> >> ________
> >>
> >>>
> >>
> >>
> >> --
> >> Dr Simon Miles
> >> Lecturer, Department of Informatics
> >> Kings College London, WC2R 2LS, UK
> >> +44 (0)20 7848 1166
> >>
> >
> >

Received on Monday, 1 August 2011 15:55:42 UTC