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

Fixed some cut/paste errors (below) in the previous post that made it
hard to read. I'll also add that we'd have similar issues if we think
about 'triggering' between processes PE1-generated-A-used-PE2 does not
allow 'triggering' to be inferred due to aggregate Bobs and triggering
transitivity would be limited by the time-relations on the processes
(PE1 could trigger PE2 after PE2 triggered PE3, so no transitivity).

 

Jim

 

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 ideas of B being partially
determined by A and transitivity - they don't mix. Aggregate Bobs cause
the trouble. 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-PE-generated: The doc notes 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