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Re: Definition of Entity

From: Luc Moreau <l.moreau@ecs.soton.ac.uk>
Date: Fri, 02 Sep 2011 14:55:26 +0100
Message-ID: <EMEW3|af8b992e4b78cc73a2320074210c8155n81EyX08l.moreau|ecs.soton.ac.uk|4E60E04E.9030805@ecs.soton.ac.uk>
To: Graham Klyne <GK@ninebynine.org>
CC: W3C provenance WG <public-prov-wg@w3.org>
Hi Graham,

Responses interleaved.

On 02/09/2011 13:00, Graham Klyne wrote:
> (Luc, This is not specifically about the issue raised, but was 
> triggered by something you wrote there.  What I am discussing is that 
> the definitions of the concepts are insufficiently clear, which may in 
> turn be why I have not previously been able to clearly express 
> agreement or disagreement with what you have proposed.)
>
> On 02/09/2011 12:38, Luc Moreau wrote:
> > So:
> > Entity: is data model construct/assertion
>
> This is new to me.  Where does it say this?  I've just looked again in 
> sections 4 and 5, and am not seeing it.

First line of section 5, explicitly, introduces " the following types of 
constructs", the first of which is Entity (section 5.1).

Section 4 states "PIDM is a provenance data model designed to express 
*representations* of the world."

And then section 5, the construct entity is defined as:

An entity *represents* an identifiable characterized thing.



>
> AFAICT, "Entity" is not mentioned at all in section 4.

And rightly so, I believe, but instead it introduces "things in the world"
>
> From what you say above, it seems that "Entity" and "Entity assertion" 
> are the same thing.  But I don't see that stated explicitly.  And if 
> true, it completely overturns what I thought we meant by "Entity".

Again sectin 4 states " PIDM is a provenance data model designed to 
express representations of the world. These representations are relative 
to an asserter, and in that sense constitute assertions characterizing 
the world.".

Hence, for Entity (and the other constructs, it's not just entity), is a 
construct representing something in the world but also an assertion made 
by an asserter.
>
> > Thing: is the thing in world
>
> I thought we were saying that "Entity" is a thing in the world about 
> which assertions have been made.  But here you seem to be saying that 
> the "Entity" *is* the assertions that have been said about a thing.

Indeed Entity is the assertion. It's about a thing in the world.

Problem is that the WG has been through multiple name changes.  Remember 
we started with stuff in the world. That's now a thing.
>
> Specifically, section 5.1 needs tlo clearly state what concept is 
> denoted by the term "Entity" - for me it does not do that.  Without 
> such a clear and well-understood statement, it's hard to make concrete 
> progress on the rest of the specification.
>
> It seems to me that the section is insufficiently clear in 
> distinguishing: language used to describe entities/things, 
> descriptions of entities/things, and the actual things described.
>
We'll take your comment into account, and see how best to address it in 
the next iteration,

Cheers,
Luc

> #g
> -- 
>
> On 02/09/2011 12:38, Luc Moreau wrote:
>> Hi Graham,
>>
>> I don't understand your comment.
>>
>> Are you discussing the difference between entity and entity assertion?
>>
>> Section 5 introduces different types of constructs.
>> Section 4 states that all representations constructed with PIDM are 
>> in fact
>> assertions by the asserter.
>>
>> So, when we write "An Entity represents an identifiable characterized 
>> thing.",
>> we refer to the construct
>> entity, which allows us in PIDM to build a representation of an 
>> identifiable
>> characterized thing.
>> That construct contains an id and attribute-value pairs.
>>
>> So:
>> Entity: is data model construct/assertion
>> Thing: is the thing in world
>>
>> I don't see what is not correct in the issue I raised.
>>
>> Luc
>>
>> On 09/02/2011 12:04 PM, Graham Klyne wrote:
>>> Luc,
>>>
>>> I'm picking up a small matter here to illustrate things I've said 
>>> previously.
>>>
>>> I notice in ISSUE 89 you say:
>>>
>>> "The conceptual model defines an entity in terms of an identifier 
>>> and a list
>>> of attribute-value pairs. It is indeed crucial for the asserter to 
>>> identify
>>> the attributes that have been frozen in a given entity."
>>>
>>> But when I look at
>>> http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#concept-Entity, 
>>>
>>> this is not what I see. What I do see is a description of an "Entity
>>> assertion" that contains a list of attribute pairs, which to my 
>>> reading is not
>>> the same thing at all.
>>>
>>> This is a part of the problem I have when I say the model document is
>>> difficult to understand.
>>>
>>> (I'm not raising this as an issue, as I've already raised a 
>>> different issue to
>>> say I think that an Entity doesn't need to be so complicated.)
>>>
>>> #g
>>
Received on Friday, 2 September 2011 13:56:04 GMT

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