RE: PROV-ISSUE-515: Data Model Section 5.1.8 [prov-dm]

Hi,

> As far as a new section on state is concerned, the Working Group has made a decision to leave this kind of material outside the prov-dm document. Some of this is actually covered in prov-constraints.

I didn't find this in prov-constraints, but I admit I am not as familiar with that doc as I am with the DM.  Could you please provide a pointer to the relevant section?

I don't think it is wrong to exclude state from the scope of PROV, but I do think there should be a defined way to express it so those that need that capability will extend the model consistently.  Explicit guidance would be beneficial, in my opinion.  Is there a term from an ontology that could be used to represent state, and recommended for use as an optional attribute if needed?

Thanks,
Bob


________________________________
From: public-prov-wg-request@listhub.w3.org [mailto:public-prov-wg-request@listhub.w3.org] On Behalf Of Luc Moreau
Sent: Wednesday, September 26, 2012 6:21 AM
To: Provenance Working Group
Cc: Provenance Working Group Issue Tracker
Subject: Re: PROV-ISSUE-515: Data Model Section 5.1.8 [prov-dm]

Dear all,

I have drafted a response to the following issue at:
http://www.w3.org/2011/prov/wiki/ResponsesToPublicComments#ISSUE-515_.28Invalidation.29

Feedback appreciated,
Regards,
Luc

ISSUE-515 (Invalidation)

  *   Original email: http://lists.w3.org/Archives/Public/public-prov-wg/2012Sep/0105.html
  *   Tracker: http://www.w3.org/2011/prov/track/issues/515
  *   Group Response
     *   "Is it possible for entities to become temporarily unavailable (e.g., for usage)? "
        *   prov-constraints states that usage precedes invalidation and follows generation. Hence, for a given entity, one cannot express that usage is not permitted over a period of time.
        *   Alternatively, one can introduce multiple specializations for the various intervals. In the following example, one defines an entity e, and two specializations. e1 is not available after 10am, and e2 before 4pm on 2011-11-16. Both e1 and e2 have an attribute ex:available indicating their availability. On the other hand, e does not have such attribute, because this aspect is not fixed during the lifetime of e.

entity(e)
entity(e1, [ex:available="yes"])
wasInvalidatedBy(e1,-,2011-11-16T10:00:00)
specializationOf(e1,e)
entity(e2,  [ex:available="yes"])
wasGeneratedBy(e2,-,2011-11-16T16:00:00)
specializationOf(e2,e)
wasDerivedFrom(e2,e1)


  *
     *   The above example shows that e has some aspects that remain constant during its lifetime (e.g. its identity), but is also allowed to have other aspects that change over time. These changing aspects cannot be expressed as attributes.
     *   There is no requirement for asserters to assert invalidation of entities
     *   Given this, the Working Group feels that the concern raised by the author is not applicable. Entities may have long lifespan, provided that they have some aspects, represented as attributes, that do not change over that lifespan. Other aspects are allowed to change. As a minimum, an entity must have a fixed entity during its lifetime.
     *   As far as a new section on state is concerned, the Working Group has made a decision to leave this kind of material outside the prov-dm document. Some of this is actually covered in prov-constraints.
  *   References:
     *   Constraint 39: http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#generation-precedes-usage
     *   Constraint 40: http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#usage-precedes-invalidation
     *   Section on entities: http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#entities--activities-and-agents
     *   Group resolution on restructuring prov-dm: http://www.w3.org/2011/prov/meeting/2012-02-23#resolution_2
     *   Discussion thread on this issue:
  *   Implemented Changes to the document: http://dvcs.w3.org/hg/prov/rev/f0e8bc2ae457
  *   Original author's acknowledgement:

[edit<http://www.w3.org/2011/prov/wiki/index.php?title=ResponsesToPublicComments&action=edit&section=36>]


On 10/09/2012 09:44, Provenance Working Group Issue Tracker wrote:

PROV-ISSUE-515: Data Model Section 5.1.8   [prov-dm]

http://www.w3.org/2011/prov/track/issues/515

Raised by: Luc Moreau
On product: prov-dm


http://www.w3.org/2011/prov/wiki/LC_Feedback#Data_Model_Section_5.1.8

ISSUE-463

See comments for 5.1.3 (incorporated by reference).

Typo: "in the last three cases" should be "in the third case".

Invalidating an entity due to a state change is going to be difficult for some people to accept, even though it may not be strictly accurate from a rigorous philosophical point of view (not all adopters of PROV will use the model this way). In fact, if this definition is applied consistently throughout the spec, then all entities will have infinitesimally short lifespans and examples (such as the car relocation example in 2.1.1) will become extremely complex. It might be worthwhile adding a section to discuss topics related to entity state, creation, etc. This would provide a way to retain these more complex points while simplifying the examples used throughout the rest of the spec.

Is it possible for entities to become temporarily unavailable (e.g., for usage)? If so, a state model for entities might be helpful.







--
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<mailto:l.moreau@ecs.soton.ac.uk>
United Kingdom                     http://www.ecs.soton.ac.uk/~lavm