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

From: Luc Moreau <l.moreau@ecs.soton.ac.uk>
Date: Tue, 23 Oct 2012 10:59:37 +0100
Message-ID: <EMEW3|5eefdea0ed3cff49fa3603b09318fa59o9MAxe08l.moreau|ecs.soton.ac.uk|50866A89.7090208@ecs.soton.ac.uk>
To: Paul Groth <p.t.groth@vu.nl>
CC: "public-prov-wg@w3.org" <public-prov-wg@w3.org>
Hi Paul,
The FAQ maybe?
Luc

On 10/22/2012 07:26 PM, Paul Groth wrote:
> Hi Luc,
>
> This is quite a nice clarification. I wonder if there's somewhere we 
> can use this without adding it to the document? I think the 
> definitions stand on their own as they now stand.
>
>
> ==Off topic==
> In general, there's a "philosophy" that's never been really stated 
> somewhere that drops out of these clarifications that I think the 
> working group shares but may not be articulated concisely in a single 
> document. I think (some) of the key points of the philosophy are:
>
> 1) Scruffy ---> Proper
> 2) Identify the fixed bits your talking about
> 3) There's multiple kinds of provenance descriptions, we provide a 
> substrate for all
> 4) PROV is extensible (it's a substrate)
>
> Maybe this should go in the overview document?
>
> cheers
> Paul
>
>
>
>
>
> On Mon, Oct 22, 2012 at 11:50 AM, Luc Moreau <l.moreau@ecs.soton.ac.uk 
> <mailto: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:
>>           o 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.
>>           o 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.
>>           o 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'.
>>           o PROV-Constraints, in its rationale section, expands on
>>             the notion of entity.
>>           o 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.
>>           o 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.
>>           o 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.
>>           o 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.
>>           o 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)
>>           o 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:
>>           o PROV constraints
>>             rationale:http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#entities--activities-and-agents
>>
>>           o entity/specialization/alternate
>>             definitions:http://www.w3.org/2011/prov/wiki/SpecializationAlternateDefinitions
>>
>>           o Resolution on
>>             entity/specialization/alternate:http://www.w3.org/2011/prov/meeting/2012-05-03#resolution_2
>>
>>           o Key Constraints
>>             definition:http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#dfn-key-constraints
>>
>>           o Key-Object constraint
>>             23:http://www.w3.org/TR/2012/WD-prov-constraints-20120911/#key-object
>>
>>       * Proposed Changes to the document:
>>           o 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."
>>           o 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 forhttp://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  <tel:%2B44%2023%208059%204487>
>     University of Southampton          fax:+44 23 8059 2865  <tel:%2B44%2023%208059%202865>
>     Southampton SO17 1BJ               email:l.moreau@ecs.soton.ac.uk  <mailto:l.moreau@ecs.soton.ac.uk>
>     United Kingdomhttp://www.ecs.soton.ac.uk/~lavm  <http://www.ecs.soton.ac.uk/%7Elavm>
>
>
>
>
> -- 
> --
> Dr. Paul Groth (p.t.groth@vu.nl <mailto:p.t.groth@vu.nl>)
> http://www.few.vu.nl/~pgroth/ <http://www.few.vu.nl/%7Epgroth/>
> Assistant Professor
> - Knowledge Representation & Reasoning Group |
>   Artificial Intelligence Section | Department of Computer Science
> - The Network Institute
> VU University Amsterdam

-- 
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
Received on Tuesday, 23 October 2012 10:00:23 UTC

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