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

From: Jim McCusker <mccusj@rpi.edu>
Date: Thu, 5 Jan 2012 16:42:36 -0500
Message-ID: <CAAtgn=QKMAygDQ1FZWYL9YxqoUwdTCoYZqt32+AFtHtd0oJwYg@mail.gmail.com>
To: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Cc: public-prov-wg@w3.org
Having read some of the relevant documentation more closely, I've realized
that my previous reading of this email was wrong, but what I see now simply
raises new questions. Hopefully this will be clearer than my last email:

1) What is the difference between an entity identifier and an entity record
2) Are identifiers allowed to be used across accounts if they are URIs?
3) If the answer to 2) is no, then how do we refer to entities that exist
outside of provenance accounts?


On Wed, Dec 21, 2011 at 4:08 PM, Luc Moreau <L.Moreau@ecs.soton.ac.uk>wrote:

> Dear all,
> Paolo and I had a discussion about identifiers, and felt that some of the
> terminology
> we used was confusing.  Hence we have made some changes, which we
> summarize here.
> 1.  The identifier that occurs in an entity record is
>    the identifier of an entity   ... and not the identifier of the record
> 2. An account allows for three things:
>        - associating asserter with assertions
>        - scoping some structural constraints (new section 7.2)
>        - scoping for the uniqueness of identifiers
> 3. Constraint:
> http://dvcs.w3.org/hg/prov/**raw-file/default/model/**
> ProvenanceModel.html#**identifiable-record-in-account<http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#identifiable-record-in-account>
>  requires that for a given entity identifier there is a most one entity
> record containing this identifier.
> We believe that with the following:
> - entity identifiers can be URIs with the usual semantic web understanding
> - entity identifiers do *not* double up as URI for entity records
> - with the above constraint, given an account and an entity URI, we can
> find an entity record for
>     this entity.
> We hope these changes will help resolve the debate on identifiers/accounts.
> No doubt that we will  discuss that at the teleconference tomorrow.
> Luc
> On 06/12/11 15:47, 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<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<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<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<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<http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#record-Account>

Jim McCusker
Programmer Analyst
Krauthammer Lab, Pathology Informatics
Yale School of Medicine
james.mccusker@yale.edu | (203) 785-6330

PhD Student
Tetherless World Constellation
Rensselaer Polytechnic Institute
Received on Thursday, 5 January 2012 21:43:25 UTC

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