Re: PROV-ISSUE-124: Constraints on Used Relation (PROV-DM and PROV-OM) [Conceptual Model]

Hi Satya,

Some attempts at answers. This is more of a test of my knowledge of the 
model so others feel free to correct.

Constraint 1
a) the constraint says "an" attribute value pair. It just means that 
there must be some. It doesn't say which because it can't. You only know 
that part (or all) of the fixed attributes were required for the process 
execution to have terminated.

b) I think this constraint is just being explicit about the definition 
of used. I would expect this as being guidance on when one can assert used.

c) PEs are historical records, so you write it down when you know it. 
But don't write it down if you don't.

Constraint 2
I think your right. To enforce the constraint, you have to have some 
time but you don't need to enforce the constraint. Also, with this 
constraint you can infer things about ordering based on generation and use .

cheers,
Paul



Provenance Working Group Issue Tracker wrote:
> PROV-ISSUE-124: Constraints on Used Relation (PROV-DM and PROV-OM)
> [Conceptual Model]
>
> http://www.w3.org/2011/prov/track/issues/124
>
> Raised by: Satya Sahoo On product: Conceptual Model
>
> The following constraints are defined for Used Relation (in PROV-DM
> document Oct 11, 2011):
>
> Constraint 1: "Given a process execution expression identified by pe,
> an entity expression identified by e, a qualifier q, and optional
> time t, if assertion used(pe,e,q) or used(pe,e,q,t) holds, then the
> existence of an attribute-value pair in the entity expression
> identified by e is a pre-condition for the termination of the
> activity represented by the process execution expression identified
> by pe."
>
> Issue: a) The above constraint may not hold for many scenarios
> involving Used relation. For example, if "table salt" was added by
> mistake to a cakeBaking PE, then Used(salt, cakeBaking PE) is true,
> but it is not clear what attribute-value must exist for "salt" to
> allow cakeBaking PE to terminate?
>
> b) Without specifying the identity, the characteristics, and how does
> this "attribute-value pair" relate to the Entity e itself (is it a
> necessary attribute-value pair for existence of e etc.) it is unclear
> how can we use this constraint.
>
> c) Further, is it necessary for the attribute-value to be explicitly
> stated prior to the start of PE instance - since with the open world
> assumption it may exist but not known to a provenance application
> before start of PE.
>
> --------------
>
> Constraint 2: "Given a process execution expression identified by pe,
> an entity expression identified by e, a qualifier q, and optional
> time t, if assertion used(pe,e,q) or used(pe,e,q,t) holds, then the
> use of the thing represented by entity expression identified by e
> precedes the end time contained in the process execution expression
> identified by pe and follows its beginning. Furthermore, the
> generation of the thing denoted by entity expression identified by e
> always precedes its use."
>
> Issue: To enforce this constraint, it will be necessary for "time"
> (or events?) to be associated with both PE and Entity instances to
> derive ordering - currently association of time is optional for both
> PE and Entity (events is not defined).
>
>
>

-- 
Dr. Paul Groth (p.t.groth@vu.nl)
http://www.few.vu.nl/~pgroth/
Assistant Professor
Knowledge Representation & Reasoning Group
Artificial Intelligence Section
Department of Computer Science
VU University Amsterdam

Received on Tuesday, 11 October 2011 19:30:51 UTC