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Re: Definition of Entity

From: Graham Klyne <GK@ninebynine.org>
Date: Fri, 02 Sep 2011 13:00:21 +0100
Message-ID: <4E60C555.70800@ninebynine.org>
To: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
CC: W3C provenance WG <public-prov-wg@w3.org>
(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.

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

 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".

 > 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.

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.


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 13:11:16 UTC

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