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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 22:07:57 +0000
Message-ID: <EMEW3|df6185cb23e818c0b226b96217698df7nB5M9I08L.Moreau|ecs.soton.ac.uk|4EDE923D.9020001@ecs.soton.ac.uk>
To: Paul Groth <p.t.groth@vu.nl>
CC: "public-prov-wg@w3.org" <public-prov-wg@w3.org>
Hi Paul,

Response are interleaved.

On 06/12/11 17:50, Paul Groth wrote:
> Hi Luc,
>
> Yes. I think that's what we wanted at least as a short cut.
>
> But can I do this?:
>
> Webpage:
> http://www.example.com/webpage
>
> entity(http://www.example.com/webpage, [])
>
> entity(http://www.example.com/webpage, [createdOn="June 4, 1998])
>
>
> I think this is not allowed in the approach in the PROV-DM

It is allowed, but the two records should be regarded as a single one, 
obtained
by union of the two.

See 
http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#identified-entity-in-account
and the example that follows.

>
>
> You would have to do:
>
> entity(http://www.example.com/webpage, [])
>
> entity(http://www.example.com/webpage/June41998, [createdOn="June 4, 
> 1998])
>
> wasComplementOf(http://www.example.com/webpage/June41998, 
> http://www.example.com/webpage)
>
>
> This means in essence you do end up minting urls for provenance, right?

Yes, this is similar to section 8 of the prov-dm document.

What is not entirely clear to me is how do we know that
http://www.example.com/webpage is the identifier of the real stuff,
whereas http://www.example.com/webpage/June41998 was minted .

Luc


> Paul
>
>
> Luc Moreau wrote:
>> Hi Paul,
>> Yes, that's what the group wanted, I believe.
>> Luc
>>
>> On 12/06/2011 05:35 PM, Paul Groth wrote:
>>> Hi Luc,
>>>
>>> Hmm, I think I remember this now..... so everything can be an entity
>>> record as soon as you type it as such.
>>>
>>> For example if I have a webpage:
>>>
>>> http://www.example.com/webpage
>>>
>>> It becomes an entity record, as soon as I do:
>>>
>>> entity(http://www.example.com/webpage, [])
>>>
>>> Is that a correct interpretation?
>>>
>>> Paul
>>>
>>>
>>>
>>>
>>> Luc Moreau wrote:
>>>> Hi Paul,
>>>>
>>>> So, OK, we could mint identifiers for entity record
>>>>
>>>>              entity(<a minted identifier here>, [ex:param="a",
>>>> ex:port="foo"])
>>>>
>>>> (Which by the way is what OPM does.)
>>>>
>>>> How do you refer to the entity now? We don't know what this record is
>>>> about.
>>>>
>>>> Luc
>>>>
>>>> On 12/06/2011 05:11 PM, Paul Groth wrote:
>>>>> So I always thought that you could mint identifiers for entity 
>>>>> records
>>>>> but you didn't have to and we supported that.
>>>>>
>>>>> But maybe that's my head inserting text where it shouldn't have
>>>>> been....
>>>>>
>>>>> Paul
>>>>>
>>>>> Luc Moreau wrote:
>>>>>> ... 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 
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>
>
Received on Tuesday, 6 December 2011 22:09:48 GMT

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