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Re: Comments on the current data model

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Tue, 11 Oct 2011 14:55:44 +0100
Message-ID: <EMEW3|8e9c701b68857db321fd57cfec9301a7n9AEym08L.Moreau|ecs.soton.ac.uk|4E944AE0.2040107@ecs.soton.ac.uk>
To: public-prov-wg@w3.org
Hi Simon,

Ah, the good old cake, ... soon cracking eggs coming back ;-)

Seriously, response interleaved.

On 10/11/2011 01:46 PM, Simon Miles wrote:
> Hi Luc,
>
>    
>> I don't understand your multiple granularities. Can you explain?
>>      
> I mean, to use an old example, that a cake may be reasonably be
> asserted to be generated by a BakeCake execution and also by a
> CookInOven execution, because the latter is a finer grained
> description than the former. The assertions could be by the same
> asserter or two different asserters.
>    

Do you mean the same entity, generated by two different process 
executions? I assume
so (separate entities wouldn't cause any problem).

The document says that if the cake was generated at two different 
moments, we really
should have two different entities (since, we should be able to expose 
some attribute
that changes or is created by the second generation).

So, really, we would have to have exact identical instant, where both 
PEs generate
this same entity. The document again says, for this to happen, we would 
have to have
synchronisation of the two PEs, and again it's not possible.

When I wrote this paragraph, I had in mind, two independent processes. 
In your
example, one PE "is included in/is a part of "  the other.  They are not 
independent.
That's only then that the granularity comes into play, and account are used
to separate different granularities.



> Before accounts are mentioned, this seems perfectly reasonable - why
> would we disallow such a description? However, we have a restriction
> that, for an account to be valid, each entity can only be generated by
> one execution within that account. This suggests to me that he
> restriction is about accounts and their validity rather than
> generation events.
>    

So, for independent PEs, the restriction by itself makes sense, and is 
intimately
linked to the nature of entities and of generation events.

For dependent PEs, then, yes,  this brings a further justification for 
accounts.

All of this needs to be clarified in the document.

Luc

> Thanks,
> Simon
>
>
>    
>> Luc
>>
>> On 10/10/2011 17:42, Simon Miles wrote:
>>      
>>> I can't see what it would mean without knowledge of accounts, or how
>>> it could be "correct without qualification". Surely it is simply not
>>> true that only one PE can generate an entity independently of
>>> accounts? Why do we not allow multiple granularities of description?
>>>
>>>        
>>
>>      
>
>
>    

-- 
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 Tuesday, 11 October 2011 13:56:19 GMT

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