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

yes, partial derivation, i.e., at the attribute level, gets in the way of transitivity. Ignoring the attributes may be a way out. 
You lose precision but save transitivity.
So you could have:

B includes B.1, B.2
B.1 derived from A     => B derived from A   (1)
C   derived from  B.2  => C derived from B   (2)
=> C derived from A    (3)

where inferences (1) and (2) are new, they "lift" derivation from attribute to whole entity, and (3) is transitivity.

"graphically":

                B
              /   \
C --> B.1   B.2 --> A   becomes C --> B --> A

Graham's example is more involved but similar:

      C                  B                 A
     /  \              /   \           /     \
  c0    c1 --> b1   b0 --> a0    a1      becomes  C --> B --> A

what do you think?

-Paolo


On 8/3/11 3:43 PM, Luc Moreau wrote:
> Jim,
>
> This counter example was already raised by Graham in PROV-ISSUE-56.
>
> My view on this is that for inference, we should ignore the attributes.
> So, definitions should be tuned to accommodate this.
>
> I don't think generation can be inferred from use/generated.
>
> Luc
>
> On 08/03/2011 03:35 PM, Myers, Jim wrote:
>>
>> Paolo, Luc,
>>
>> Both clearly have to work the same way if we don’t know about PE internals.
>>
>> However, I still have some concern about the idea that B is partially determined by A and transitivity don’t mix. But it doesn’t 
>> address aggregate Bobs. If B has two parts, B.1, and B.2 and B.1 is derived from A, so that B is derivedFrom A, we could also 
>> have C derived from B.2 (therefore C derivedfrom B) and transitivity would break -  C is not derivedfrom A. (I see this as 
>> ~analogous to the issue of derivation being inferable from used/generated: The doc does note that if B was generated before A was 
>> used, derivation cannot be true, so you can’t infer derivation from used-PE-generated structures. This is because PEs can have 
>> temporal parts- they could be an aggregate process. There are analogous issues because Bobs can have spatial parts/be aggregate 
>> objects. This means you can’t infer across generated-Bob-used structures either and transitivity allows this.)
>>
>> I think that boils down to there only being two self-consistent definitions for derivation –
>>
>> It is inferable from used/generated and is transitive
>>
>> It implies partial determination, is only assertable, and is not transitive
>>
>> I think we can pick either or both, but right now it still looks like we mix the idea that there’s some real partial 
>> determination with transitivity in ways that can break.
>>
>>   Jim
>>
>> *From:*public-prov-wg-request@w3.org [mailto:public-prov-wg-request@w3.org] *On Behalf Of *Paolo Missier
>> *Sent:* Wednesday, August 03, 2011 8:36 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]
>>
>> JIm
>>
>> we have established that isDerivedFromInMultipleSteps is also transitive. I hope this is fine.
>>
>> The point of having the relation is that, as Luc explained here below, in this case the "pe introduction rule"(*) should not be 
>> used.
>> In other words, isDerivedFromInMultipleSteps simply means that, according to the asserter, more than one pe is required to 
>> explain the derivation (but we don't know how many).
>>
>> I can see that your objection is valid, however, in the sense that I can make up one single pe that encompasses an arbitrary 
>> number of steps.
>> The problem is that we haven't said anything about the nature of the activity represented by a pe. Unless we say something about 
>> their granularity and composition, any pe can represent any aggregation of "elementary" activities.
>>
>> -Paolo
>>
>> (*) if*isDerivedFrom(e1,e0)*holds, then there exists a process execution*pe*, and roles*r0*,*r1*, such 
>> that:*isGeneratedBy(e1,pe,r1)*and*uses(pe,e0,r0)*.
>>
>>
>> 8/2/11 3:08 AM, Myers, Jim wrote:
>>
>>   
>>
>>     It's not that pe is atomic or not. It's that there is a tight link between
>>
>> the derivation and  the process execution.
>>   
>>
>>     isDerivedFromInMultipleSteps is silent about that link.
>>
>>   
>> If B isDerivedInMultipleSteps from A, can't I (a second witness) always make up a single process that encompasses all steps? Would it then be OK (for me, the second witness making up this account) to claim a direct B isDerivedFrom A. Then I can do transitive closure over such relationships? And then recognize that there were multiple steps, thus making isDerivedInMultipleSteps transitive too?
>>   
>>
>>     I am not trying to infer derivation beyond transitive closures.
>>
>>   
>> I don't see how the definitions given allow one to be transitive and one not to be. If the only difference between the two was an implication of how much the witness knew about what happened (one step or multiple), but both were transitive, I wouldn't be confused (I might still argue that we don't need the distinction).
>>   
>> Cheers,
>>   Jim
>>   
>>   
>> Regards,
>> Luc
>>
>
> -- 
> 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 Kingdomhttp://www.ecs.soton.ac.uk/~lavm


-- 
-----------  ~oo~  --------------
Paolo Missier - Paolo.Missier@newcastle.ac.uk, pmissier@acm.org
School of Computing Science, Newcastle University,  UK
http://www.cs.ncl.ac.uk/people/Paolo.Missier