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Re: PROV-ISSUE-85 (What-is-Entity): Definition of Entity is confusing, maybe over-complex [Conceptual Model]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Mon, 05 Sep 2011 15:53:57 +0100
Message-ID: <EMEW3|62f07e8565ec858bfc6909ae7f4e746dn84Fs108L.Moreau|ecs.soton.ac.uk|4E64E285.6080003@ecs.soton.ac.uk>
To: public-prov-wg@w3.org
Hi Graham, Jim, and Simon,

Following the discussion this WE, Paolo and I have revised  the 
definition of entity.
Before editing the document, we would like to get your feedback.

General assumption (to appear in section 4):  in the real world, we find:
    - identifiable characterized things, their situation in the world
    - activities
    - events


Revised section 5.1

In PIDM, an entity construct is a representation of an identifiable 
characterized thing.

An instance of an entity construct, expressed as entity(id, [ attr:
val, ...]) in the Provenance Abstract Syntax Notation:
- contains an identifier id, denoting a characterized thing
- contains a set of attribute-value pairs [ attr: val, ...], representing
   this characterized thing's situation in the world.

The assertion of an instance of an entity construct , entity(id, [ attr: 
val, ...]), states, from a given asserter's viewpoint, the existence of 
an identifiable characterized thing, whose situation in the world is 
represented by the attribute-value pairs, which remain unchanged during 
a characterization interval, i.e. a continuous interval between two 
events in the world (which may collapse into a single instant).

Example: <same example>
... states the existence of a thing of type File and location 
/shared/crime.txt,  and creator alice, denoted by identifier e0, during 
some characterization interval.

Further properties:
- If an asserter wishes to characterize a thing with same 
attribute-value pairs over several intervals, then they are required to 
assert multiple entity assertions, each with its own identifier.

- There is no assumption that the set of attributes is complete and that 
the attributes are independent/orthogonal of each other.


On 09/01/2011 05:32 PM, Provenance Working Group Issue Tracker wrote:
> PROV-ISSUE-85 (What-is-Entity): Definition of Entity is confusing, maybe over-complex [Conceptual Model]
> http://www.w3.org/2011/prov/track/issues/85
> Raised by: Graham Klyne
> On product: Conceptual Model
> See also: http://lists.w3.org/Archives/Public/public-prov-wg/2011Aug/0383.html
> Section 5.1.
> The definition of "Entity" seems to introduce un-needed complications.  I don't see anything here that fundamentally distinguishes an entity from anything that can be named, i.e. a web resource.
> I don't see what useful purpose is served by the insistence on "characterized thing".
> This section seems to spend more effort describing "entity assertion" is is apparently a different concept, but not formally part of the model.  There is some sense that an entity must have associated entity assertions... but I can't see why this is needed, and indeed it may be not possible to enforce this idea in RDF's open world model.
> There's been talk of Entities being part of the occurrent vs continuant distinction, but I'm not seeing that explained.
> Suggest:  why not just have an entity as an identifiable thing, and build the rest around that?  What would break with this approach?

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 Monday, 5 September 2011 14:54:27 UTC

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