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Re: PROV-ISSUE-105: 5.3.1 Generation (current version of the conceptual model document) [Conceptual Model]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Mon, 07 Nov 2011 11:29:56 +0000
Message-ID: <EMEW3|833330a2def1b1b4bdb92422077a85d0nA6BYw08L.Moreau|ecs.soton.ac.uk|4EB7C134.70503@ecs.soton.ac.uk>
To: public-prov-wg@w3.org
Hi Satya,

Responses interleaved.   I am also proposing to close this issue.

On 09/28/2011 05:16 PM, Provenance Working Group Issue Tracker wrote:
> PROV-ISSUE-105: 5.3.1 Generation (current version of the conceptual model document) [Conceptual Model]
>
> http://www.w3.org/2011/prov/track/issues/105
>
> Raised by: Satya Sahoo
> On product: Conceptual Model
>
> Hi,
> My review comments for 5.3.1 Generation in the current version of the conceptual model document:
>
> 5.3.1 Generation
> =====
> 1. In PROV-DM, a generation expression is a representation of a world event, the creation of a new characterized thing by an activity. This characterized thing did not exist before creation.
>
> Issue: The "characterized thing" in the above statements is Entity or some other resource?
>    

Now,  we have defined entity as an identifiable characterized thing. So, 
the statements has become:

In PROV-DM, a generation record is a representation of a world event, 
the creation of a new entity by an activity. This entity did not exist 
before creation. The representation of this event encompasses a 
description of the modalities of generation of this entity by this activity.


> 2. contains a generationQualifier q that describes the modalities of generation of this thing by this activity
>
> Issue: How is this qualifier distinct from specialization of the generation property?
>    

I think the work on prov-o now answers this question.

> 3. The first one is available as the first value on port p1, whereas the other is the second value on port p1.
>
> Issue: As we discussed during the telcon on  Sept 15 [1] and in email thread (Subject: Roles, initiated by Paolo on Sept 15), the "qualifier" if any are on the entity and PE and not on the relation. In the above statement, port p1 is qualifier for either the entities e1, e2 (they were generated on that particular port) or the PE pe1 (it was using that port for listening/responding). Hence, the qualifiers are on the "class" and not the "relation".
>
> [1] http://www.w3.org/2011/prov/meeting/2011-09-15
>    

I think the work on prov-o also answers this comment.

> 4. If two process executions sequentially set different values to some attribute by means of two different generate events, then they generate distinct entities.
>
> Issue: This is an incorrect statement. Setting values of an entity at different points of time cannot be equated to generating new entities. For example, we don't generate a new human being everytime a PE changes the value of their age. pe1 sets Person X age = 5 years in 2005 and pe2 sets Person X age = 10 years in 2010 then they are not generating new person (within an account or across accounts).
>    

Remember that an entity is a perspective on a thing.
So, here, we can have multiple perspectives:

e1 Luc
e2 Luc at age=5
e3 Luc at age=10

e3 and e2 have a same attribute name age, but different values. So they 
must be different entities,i.e. perspectives, over human being e1.

> 5. Alternatively, for two process executions to generate an entity simultaneously, they would require some synchronization by which they agree the entity is released for use; the end of this synchronization would constitute the actual generation of the entity, but is performed by a single process execution.Given an entity expression denoted by e, two process execution expressions denoted by pe1 and pe2, and two qualifiers q1 and q2, if the expressions wasGeneratedBy(e,pe1,q1) and wasGeneratedBy(e,pe2,q2) exist in the scope of a given account, then pe1=pe2 and q1=q2.
>
> Issue: If two sculptors collaborate on creating a human figurine statue entity e1: sculptor A by PE pe1 creates the arms and legs of e1 and sculptor B by PE pe2 creates the head and upper-body part of e1 then both pe1 and pe2 create e1. They may or may not be synchronized. How can we infer that pe1 = pe2 (whether in one account or across accounts)?
>    

I think you've articulated well the case that A and B create different 
parts.  If they do this at different times, you will have
statue without head, statue with head without leg, statue with head with 
leg.

The constrained with accounts on generation-unicity is enforcing some 
structure in the provenance records, so that if really pe1<>pe2, then
they should generate the statue in different records.

I am proposing, in the end, to follow Simon's proposal, and move this in 
an entirely different section.
> 6. Given an identifier pe for a process execution expression, an identifier e for an entity expression, qualifier q, and optional time t, if the assertion wasGeneratedBy(e,pe,r) or wasGeneratedBy(e,pe,r,t) holds, then the values of some of e's attributes are determined by the activity represented by process execution expression identified by pe and the entity expressions used by pe. Only some (possibly none) of the attributes values may be determined since, in an open world, not all used entity expressions may have been asserted. [PROV:0002]
>
> Issue: This constraint is confusing (maybe even contradictory) - some or none attributes may be determined? Further, there is no specification or mechanism defined to identify which attributes were determined by the PE? the constraint does not provide any new information (even as a constraint) regarding generation.
>    

We have decided to drop this constraint at the last teleconference.
> 7. If an assertion wasGeneratedBy(x,pe,r) or wasGeneratedBy(x,pe,r,t), then generation of the thing denoted by x precedes the end of pe and follows the beginning of pe.
>
> Issue: Suggest rewording this: given the assertion that "an Entity e1 was generated by a PE pe1" then "the Entity e1 did not exist before start of PE pe1".
>
>
>
>    
This would be an entirely different meaning that is not the same as the 
one intended.

Cheers,
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 Kingdom                     http://www.ecs.soton.ac.uk/~lavm
Received on Monday, 7 November 2011 11:30:55 GMT

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