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

From: Khalid Belhajjame <Khalid.Belhajjame@cs.man.ac.uk>
Date: Tue, 23 Oct 2012 10:46:55 +0100
Message-ID: <CAANah+HMtWWumgK5BAoHbTygh=Xgd-jWb54zh+3uExymnnShkA@mail.gmail.com>
To: Paul Groth <p.t.groth@vu.nl>
Cc: Luc Moreau <l.moreau@ecs.soton.ac.uk>, "public-prov-wg@w3.org" <public-prov-wg@w3.org>
HI Paul,

Yes, I agree, that's why I said that I am happy with the response, I
dont think we should try do anything more.

khalid

On 23 October 2012 10:08, Paul Groth <p.t.groth@vu.nl> wrote:
> 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 09:47:23 UTC

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