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Re: PROV-ISSUE-183 (prov-dm-identifiers): identifiers in prov-dm [prov-dm]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Tue, 06 Dec 2011 17:04:40 +0000
Message-ID: <EMEW3|2d962b24a8a18b34f649d4f2b8f0292dnB5H4i08L.Moreau|ecs.soton.ac.uk|4EDE4B28.5030204@ecs.soton.ac.uk>
To: Paul Groth <p.t.groth@vu.nl>
CC: Provenance Working Group WG <public-prov-wg@w3.org>
... the conclusion issue ;-)

No, we have no formal decision on this.

We wrote this in the prov-dm document a long time ago (before fpwd), and 
we have
been refining it over time.

I think it's an inevitable consequence of two key decisions:
- distinguishing entities (in the world) from entity records (in the 
provenance)
- not mandating the minting of new URIs for entity records
     (no formal decision on this, but I think we have support for it, since
      we want to minimize the effort to generate provenance)

Luc


On 12/06/2011 04:56 PM, Paul Groth wrote:
> Hi Luc,
>
> Do you have a pointer to wear we reached the consensus about the dual 
> role of identifiers?
>
> Thanks,
> Paul
>
> Provenance Working Group Issue Tracker wrote:
>> PROV-ISSUE-183 (prov-dm-identifiers): identifiers in prov-dm
>> [prov-dm]
>>
>> http://www.w3.org/2011/prov/track/issues/183
>>
>> Raised by: Luc Moreau On product: prov-dm
>>
>>
>> Hi,
>>
>> It think that it is now time to have a proper debate about
>> identifiers in prov-dm since comments are regularly expressed about
>> them. I have raised this issue about this topic so that we can track
>> the conversation properly. Our hope is to reach consensus on this
>> topic by the time of the third working draft.
>>
>> First, in the fpwd, there was a mention of "qualified identifier"
>> (appearing in a note see [1]).  We have removed this term from the
>> second working draft.
>>
>> Second, the complementarity record now explicitly allows for linking
>> entity records across accounts. Its syntax allows for two accounts to
>> be named.
>>
>> Third, identifiers for entities in prov-dm have a dual role [3]. An
>> entity has got an id (typically given by an application). An entity
>> record --- i.e. what we say about an entity in a provenance record
>> --- also has an id. There is a consensus that we shouldn't mint
>> identifiers for provenance records. Hence, the identifier of the
>> entity record is defined to be the same as the identifier of the
>> entity.
>>
>> The consequence of this is that two entity records in different
>> accounts may have the same identifier: they may say different things
>> about the same entity.  For example, the document ex:doc was
>> generated by latex in account1, while in account 2, ex:doc is
>> described to be the result of a survey of a field by different
>> authors.
>>
>> This explains why we needed the complementarity record to name the
>> accounts as well. This assumes that account names need to be named
>> uniquely (see [4]).
>>
>> So, entity records identifiers are scoped to accounts.  Note, I said
>> entity *records*, not entities. Hence, we are not breaking the
>> semantic web approach: an entity is a resource and is denoted by a
>> URI, and this remains true in all accounts. (I guess that from a
>> semantic web perspective we are not looking at a provenance record as
>> resource, since we don't have a global URI to name it.) Finally, we
>> allow for accounts to be nested hierarchically; this fits nicely with
>> abstraction in provenance records. Again, see [4].
>>
>> Can you express your views about this approach, as currently defined
>> in the second draft of prov-dm?
>>
>> Thanks, Luc
>>
>> [1]
>> http://www.w3.org/TR/2011/WD-prov-dm-20111018/#expression-identifier
>> [2]
>> http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#record-complement-of 
>>
>>
>>
> [3] 
> http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#record-Entity 
>
>> [4]
>> http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#record-Account 
>>
>>
>>
>>
>>
>

-- 
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, 6 December 2011 17:05:30 UTC

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