- From: Paul Groth <p.t.groth@vu.nl>
- Date: Mon, 22 Oct 2012 20:26:44 +0200
- To: Luc Moreau <l.moreau@ecs.soton.ac.uk>
- Cc: "public-prov-wg@w3.org" <public-prov-wg@w3.org>
- Message-ID: <CAJCyKRoK6KU2QX4XrbRRfZ_Oe-BcRSgO18-DSwkyLPrJaKUUkA@mail.gmail.com>
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>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 Monday, 22 October 2012 18:27:13 UTC