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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 22:22:15 +0100
Message-ID: <EMEW3|a4a89b7e987e5af6cdc2e5f3afc93aaen84MNc08L.Moreau|ecs.soton.ac.uk|4E653D87.1030305@ecs.soton.ac.uk>
To: Graham Klyne <GK@ninebynine.org>
CC: public-prov-wg@w3.org
Hi Graham,

Actually, this whole thread of discussion, and separate emails with Paolo,
make me think that it's more appropriate:

1. To present the data model as a representation of the world.
     Hence, an entity is a *representation* of an identifiable 
characterized thing,
    or a process execution is a *representation* of an activity.


2. To explain that representations of the world can be asserted by 
asserters, and what this means in terms
      of existence of stuff in the world (from the asserter's viewpoint).
     Note that the model also allows for some of the representations to 
be inferred (as opposed to asserted).
     For instance, agents can be inferred or asserted.

Hence, for uniformity, I think it's more appropriate to talk about 
constructs of a data model.
Where it is clear that a construct can only be asserted, then, use the 
term assertion.

Further comment interleaved.

On 05/09/11 21:36, Graham Klyne wrote:
> Luc,
>
> I think it's better, but:
> (a) I still think the term "Entity" doesn't quite reflect what is 
> being defined, and
> (b) I still think the first sentence doesn't really tackle what an 
> Entity [Assertion] actually *is* - your more oblique approach via 
> "representation" leaves me, as a reader, guessing at what it is you 
> really mean to convey.
>
> I still think that starting out with something like:
>
> "A (BOB) is an assertion about an identifiable characterized thing" 
> (if you'll excuse the resurrection of "BOB" here) gets the key 
> information in front of the reader in a way that is less easily 
> overlooked.  Subsequent text can explain in more detail, as you do, 
> the details of what this actually means.

I think this is very misleading. A Bob (hey, long time no see!) is not 
an arbitrary assertion *ABOUT* an identifiable characterized thing.
In fact, when you assert a Bob, you assert the *existence* of an 
identifiable characterized thing (... with attributes ... over ... 
interval, etc).

Cheers,
Luc


>
> #g
> -- 
>
>
> On 05/09/2011 15:53, Luc Moreau wrote:
>> 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
>>
>> Cheers,
>> Luc
>>
>>
>>
>> -----
>> 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.
>>
>> Cheers,
>> Luc
>>
>>
>> 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?
>>>
>>>
>>>
>>
Received on Monday, 5 September 2011 21:24:06 GMT

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