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Re: PROV-ISSUE-462 (entity-definition-precision): Definition o entity may be too liberal [prov-dm]

From: Paul Groth <p.t.groth@vu.nl>
Date: Tue, 23 Oct 2012 11:08:46 +0200
Message-ID: <CAJCyKRoJK7n6q-m-G-DfxmDo271ua4S9wyZxLnnHYSy9azzJ=A@mail.gmail.com>
To: Khalid Belhajjame <Khalid.Belhajjame@cs.man.ac.uk>
Cc: Luc Moreau <l.moreau@ecs.soton.ac.uk>, "public-prov-wg@w3.org" <public-prov-wg@w3.org>
Hi Khalid,

I think entity is pretty loose so it's going to be hard to misuse... :-)
but I think that was the whole point.

cheers
Paul


On Tue, Oct 23, 2012 at 10:52 AM, Khalid Belhajjame <
Khalid.Belhajjame@cs.man.ac.uk> wrote:

> The response to this issue is thorough and I think we should go ahead with
> it.
> However, I think that the reviewer is right: identifying what an
> entity is may be difficult for prov users (compared for example to
> Activity which is simple and clear), and I am anticipating that the
> entity concept will be mis-used more than others.
>
> Thanks, khalid
>
> On 22 October 2012 10:50, Luc Moreau <l.moreau@ecs.soton.ac.uk> wrote:
> > Dear all,
> >
> > I have drafted a response to the following issue. See
> >
> http://www.w3.org/2011/prov/wiki/ResponsesToPublicComments#ISSUE-462_.28Definition_of_Entity.29
> >
> >  I will implement the changes once I have a confirmation
> > the group is happy with them, and they satisfactorily address the issue.
> >
> >
> > ISSUE-462 (Definition of Entity)
> >
> > Original email:
> >
> http://lists.w3.org/Archives/Public/public-prov-comments/2012Jul/0009.html
> > Tracker: http://www.w3.org/2011/prov/track/issues/462
> > Group Response:
> >
> > The term 'entity' is intentionally defined in a liberal manner to avoid
> > restricting users expressivity. Obviously, it shouldn't be too liberal,
> > otherwise it would be all encompassing, without clear semantics.
> > The term 'entity' (and associated notions such as 'alternate',
> > 'specialization') have been the subject of intense debate by the Working
> > Group, and the definition reflects the compromise reached by the Working
> > Group.
> > The term 'aspect' is not used here with a technical meaning and should be
> > understood with its dictionary meaning 'A particular part or feature of
> > something'.
> > PROV-Constraints, in its rationale section, expands on the notion of
> entity.
> > While an object/thing may change over time, an entity fixes some aspects
> of
> > that thing for a period of time (in between its generation and
> > invalidation). As opposed to other models of provenance (such as OPM), an
> > entity is not an absolute state snapshot. Instead, it is a kind of
> partial
> > state, just fixing some aspects. The rationale for this design decision
> is
> > that it is quite challenging to find absolute state snapshots that do not
> > change: the location of a file on a cloud changes, the footer of this Web
> > page changes (as more people access it), etc. Hence, by allowing some
> > aspects (as opposed to all) to be fixed, the PROV concept of 'entity' is
> > easy to use.
> > We distinguish an 'aspect' from an 'attribute'. An attribute-value pair
> > represents additional information about an entity (or activity, agent,
> > usage, etc). In the case of an entity, attribute-value pairs provide
> > descriptions of fixed aspects. So, the term 'aspect' refers to
> properties of
> > the thing, whereas the term 'attribute' refers to its description in
> PROV.
> > PROV does *NOT* assume that all fixed aspects are described by
> > attribute-value pairs. So, there may be some fixed aspects that have not
> > been described. Obviously, without description, it's difficult to query
> or
> > search over them.
> > According to PROV Constraint key-object (constraint 23), an entity has a
> set
> > of attributes given by taking the union of all the attributes found in
> all
> > descriptions of that entity. In other words, PROV does not allow for
> > different attribute-value pairs to hold in different intervals for a
> given
> > entity.
> > The attribute-value pairs of an entity provide information for some of
> the
> > fixed aspects of an entity.
> >
> > This point may not have been clear, and requires text modification. (see
> > below)
> >
> > A specific attribute of an entity is its identity. It is also assumed
> that
> > it holds for the duration of the entity lifetime.
> >
> > This point may not have been clear, and requires text modification. (see
> > below)
> >
> > References:
> >
> > PROV constraints rationale:
> >
> http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#entities--activities-and-agents
> > entity/specialization/alternate definitions:
> > http://www.w3.org/2011/prov/wiki/SpecializationAlternateDefinitions
> > Resolution on entity/specialization/alternate:
> > http://www.w3.org/2011/prov/meeting/2012-05-03#resolution_2
> > Key Constraints definition:
> >
> http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#dfn-key-constraints
> > Key-Object constraint 23:
> > http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#key-object
> >
> > Proposed Changes to the document:
> >
> > http://www.w3.org/TR/prov-dm/#entity.attributes: instead of
> "representing
> > additional information about this entity." write "representing additional
> > information about the fixed aspects of this entity."
> > http://www.w3.org/TR/prov-dm/#term-identifier: add the following.
> >
> > Entity, Activity, and Agent have a mandatory identifier. Two entities
> (resp.
> > activities, agents) are equal if they have the same identifier.
> > Generation, Usage, Communication, Start, End, Invalidation, Derivation,
> > Attribution, Association, Delegation, Influence have an optional
> identifier.
> > Two generations (resp. usages, communications, etc.) are equal if they
> have
> > the same identifier.
> >
> >
> >
> >
> > Luc
> >
> >
> >
> > On 07/25/2012 08:16 AM, Provenance Working Group Issue Tracker wrote:
> >
> > PROV-ISSUE-462 (entity-definition-precision): Definition o entity may be
> too
> > liberal [prov-dm]
> >
> > http://www.w3.org/2011/prov/track/issues/462
> >
> > Raised by: Paul Groth
> > On product: prov-dm
> >
> > This is the issue for
> >
> http://lists.w3.org/Archives/Public/public-prov-comments/2012Jul/0009.html
> >
> > from Jacco van Ossenbruggen
> >
> >
> >
> >
> > --
> > 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
> >
>
>


-- 
--
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
- The Network Institute
VU University Amsterdam
Received on Tuesday, 23 October 2012 09:09:14 UTC

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