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Re: PROV-ISSUE-145 (Tlebo): qualified identifiers may not work well with named graphs [Data Model]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Tue, 08 Nov 2011 16:24:53 +0000
Message-ID: <EMEW3|12940e7c3b470164c49f97f40783b826nA7GOy08L.Moreau|ecs.soton.ac.uk|4EB957D5.5040908@ecs.soton.ac.uk>
To: Timothy Lebo <lebot@rpi.edu>
CC: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Tim,

The notion of scope is discussed in the account section, but maybe 
deserves a subsection
on its own.  Relevant wording include:

- Account records constitute a scope for identifiers.
- An identifier within the scope of an account is intended to denote a 
single record.
- Account records can be nested since an account record can occur among 
the records being wrapped by another account.
- Account records constitute a scope for identifiers. Since accounts can 
be nested, their scope can also be nested; thus, the scope of 
identifiers should be understood in the context of such nested scopes. 
When a record with an identifier occurs directly within an account, then 
its identifier denotes this record in the scope of this account, except 
in sub-accounts where records with the same identifier occur.

Do you have specific questions? We are not trying to suggest that 
resource URIs are not global.
There are, in the RDF sense. However, the records we create for 
provenance, reuse those URIs, to
also identify those records.  Given we can create multiple records about 
a same URI, we need to
manage name clashes.

Luc


On 11/08/2011 03:36 PM, Timothy Lebo wrote:
> On Nov 7, 2011, at 3:57 AM, Luc Moreau wrote:
>
>    
>> Hi Tim,
>>
>> Resources are identified by a URI. It has been suggested that perspectives we
>> take over a given resource, i.e. entities, may use the resource URI as their own
>> identifier (provided this does not result in clash names, as suggested in last section
>> of prov-dm document).
>>
>> Hence, two different entities could be asserted by two different asserters in different accounts,
>> and both may have chosen the same URI to identify them.
>>
>> If we want to avoid this
>>      
> I'm not trying to avoid this.
>
>    
>> , then it must be a requirement that new URIs are minted for all
>> entities.
>>      
> This sounds like a bad requirement.
>
>    
>> But I thought the WG wanted to move away for that, since it prevents lightweight assertions
>> of provenance.
>>      
> Agreed!
>
>    
>> So, the minting burden, i think, is put at the level of accounts.
>>      
> I think I agree here. You mean that when someone mentions an Entity in an Account, they should consider the ramifications of minting a new unknown vs. reusing an entity they say from somewhere else?
>
>    
>> BTW, prov-dm is currently not suggesting that, since it says that account identifiers are also scoped,
>>      
>
> I've run into problems with "scoped" a few times and I know others have, too.
> Can something be added to DM to clarify what it means?
>
>
>
>    
>> but I think this is not good.
>>      
>
> I couldn't say without a better understanding of "scoped".
>
>
>
> Thanks,
> Tim
>
>
>
>
>    
>> Luc
>>
>> On 11/06/2011 11:49 PM, Tim Lebo wrote:
>>      
>>> Hi, Luc!
>>>
>>> Sent from my iPhone
>>>
>>> On Nov 6, 2011, at 17:44, Luc Moreau<L.Moreau@ecs.soton.ac.uk>   wrote:
>>>
>>>
>>>        
>>>> Hi Tim,
>>>>
>>>> We need to explore this in detail.
>>>> To me, it is crucial to be able to assert that entity e1 in account acc1 is complementOf entity e2 in acc2.
>>>>
>>>>          
>>> Absolutely.
>>>
>>>
>>>        
>>>> How do you propose doing this?
>>>>
>>>>          
>>> Would the one triple
>>>
>>> :e1 prov:wasComplementOf :e2 .
>>>
>>> work? This would stand independent of what account the entities are in -- which gets to the point I was making that the asserter needs to make distinct URIs and not depend on some account-based scoping mechanism to establish its identity.
>>>
>>> Perhaps I am misinterpreting DM again from a "too RDF" perspective like the literal versus URI discussions earlier today.
>>>
>>> Best,
>>> Tim
>>>
>>>
>>>        
>>>>
>>>> Professor Luc Moreau
>>>> Electronics and Computer Science
>>>> University of Southampton
>>>> Southampton SO17 1BJ
>>>> United Kingdom
>>>>
>>>> On 6 Nov 2011, at 21:24, "Timothy Lebo"<lebot@rpi.edu>   wrote:
>>>>
>>>>
>>>>          
>>>>> By "appropriately scoped", I mean "predefined, consciously selected; URIs".
>>>>>
>>>>> the note "refer to an identifier in the scope of a given account" sounds like we are going to permit lazy naming that can be computed in the future, which current named graph implementations do not support.
>>>>>
>>>>> -Tim
>>>>>
>>>>>
>>>>>
>>>>> On Nov 6, 2011, at 2:32 AM, Luc Moreau wrote:
>>>>>
>>>>>
>>>>>            
>>>>>> Hi Tim,
>>>>>>
>>>>>> What do you mean by appropriately scoped?
>>>>>>
>>>>>> Luc
>>>>>>
>>>>>>
>>>>>>
>>>>>> I propose that we require the asserters to define appropriately-scoped URIs for their identifiers. Letting them be lazy up front will cause headaches when actually trying to use it.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>              
>>>>>
>>>>>            
>>>>
>>>>          
>> -- 
>> 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
>>
>>
>>      
>    

-- 
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, 8 November 2011 16:25:40 UTC

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