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

From: Provenance Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Tue, 11 Oct 2011 18:24:48 +0000
To: public-prov-wg@w3.org
Message-Id: <E1RDh0S-00070x-0z@barney.w3.org>

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.

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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).
Received on Tuesday, 11 October 2011 18:24:49 GMT

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