- From: Timothy Lebo <lebot@rpi.edu>
- Date: Wed, 16 Nov 2011 10:52:38 -0500
- To: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
- Cc: public-prov-wg@w3.org
On Nov 7, 2011, at 7:13 AM, Luc Moreau wrote: > Hi Satya, > > Responses interleaved. > > On 10/11/2011 07:24 PM, 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. >> >> > > We now have decided to drop this constraint. So, I guess, this answers your concern ;-) +1 for dropping. Constraint 1 above seemed concerning. >> -------------- >> >> 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). >> >> >> > > We are proposing to make a distinction between > - inferences > - so-called constraints that are there for the purpose of interpretation > - constraints that need to be enforced in the data model to be "well formed". I think it would be useful to draw that distinction in DM, to help interpretation of the document. Would this be possible? Thanks, Tim > > Constraint 2, is of the second kind, here to provide an interpretation to the data model. > It is not necessarily enforceable. > > Would this address your concerns? > > If so, can the issue be closed? > > Thanks, > Luc
Received on Wednesday, 16 November 2011 15:53:42 UTC