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Re: Definition of Entity

From: Graham Klyne <GK@ninebynine.org>
Date: Fri, 02 Sep 2011 15:35:46 +0100
Message-ID: <4E60E9C2.7000207@ninebynine.org>
To: Luc Moreau <l.moreau@ecs.soton.ac.uk>
CC: W3C provenance WG <public-prov-wg@w3.org>
Luc,

We could (and maybe should) continue to bat comments about the form of words 
used, but my main point is that *this reader* (i.e. me) finds it hard to 
understand what you are defining.  Now maybe I'm atypically stupid compared with 
the audience who will need to use this document - I can live with that, but of 
course if I really believed it I wouldn't be pushing at this.


Specific problems to consider:

Generally, the definition of such a fundamental concept as "Entity" is too 
convoluted:  your own explanation refers to text spread across two sections, 
with several intervening/mediating concepts.

A lot in your description hinges on one occurrence of the word "represents" 
(section 5.1), but in English this word can be used in many ways, and is not 
really a precise.  For example, the Oxford English dictionary definition 
(http://oxforddictionaries.com/definition/represent) indicates 10 different 
senses in which this word can be used.

I think the definition in section 5.1 should be as self contained as reasonably 
possible: that's where I look to find out what an "Entity" is.  If you need to 
refer to descriptions given elsewhere, then I think they should be referenced 
explcitly.  What I really want to find is a statement that starts "An entity 
*is* ..."

...

You say

 > 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.

(a) your use of "hence" suggests that the second paragraph follows as a natural 
consequence of the first.  I can't see that.  The first paragraph doesn't use 
the term "Entity" so I can't see any natural conclusions about about "entities" 
flowing from it.

(b) in the second paragraph, the notion of an entity as a denoting term (which 
is what I guess you mean by "represent" in this context) and also as a 
contextualized assertion (in the sense of being a claim made by a particular 
person) seems all wrong to me - I think there's a confusion between terms, 
language and denoted things here.

(c) If what is being described is an assertion *about* a thing, then I think the 
term "Entity" is completely misleading.  "Assertion" would be better, IMO.

#g
--


On 02/09/2011 14:55, Luc Moreau wrote:
> 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 16:37:46 GMT

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