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Re: Contextualization ---> Optional bundle in Specialization

From: Graham Klyne <Graham.Klyne@zoo.ox.ac.uk>
Date: Wed, 27 Jun 2012 23:31:01 +0100
Message-ID: <4FEB89A5.2000007@zoo.ox.ac.uk>
To: Paul Groth <p.t.groth@vu.nl>
CC: Luc Moreau <L.Moreau@ecs.soton.ac.uk>, Provenance Working Group WG <public-prov-wg@w3.org>
On 27/06/2012 19:21, Paul Groth wrote:
> So the use case is the issue?
>
> I really don't get how the example breaks any semantics. Sorry...
>
> So I think that your approach to allowing a qualified specialization would be fine with me especially if we add a inBundle predicate that identifies a bundle. but Tim was really really against this because of the increased number of triples.

Well, my proposal tries to avoid adding a *specific* "in bundle" qualification 
at this time, just a hookm for introducing one when we know how the semantics 
could work.

I think the "increased number of triples" is symptomatic of the problem here. 
The situation might (only "might" - I'm not sure) be addressed by reifying the 
inclusion of statements about an entity in a bundle ... and, as we have seen in 
the past, and more recently with the qualified relation patterns in PROV-O, 
reifying stuff within the RDF model does tend to cause an explosion of triples.

To reiterate:  I think the appropriate and long-term solution here is to have 
proper semantics for RDF datasets, and then to build the contextualization of 
provenance around those semantics.  So far, the RDF group hasn't delivered any 
dataset semantics, which is unfortunate.

#g
--

>
> On Jun 27, 2012, at 19:48, Graham Klyne<graham.klyne@zoo.ox.ac.uk>  wrote:
>
>> On 27/06/2012 18:39, Paul Groth wrote:
>>> Hi Graham
>>>
>>> These are two different urls so they identify different things.
>>
>> Not necessarily,  There is no unique-name assumption in RDF.  They could denote
>> the same thing.
>>
>>> The fact that we add some properties like bundle or specializationof doesn't break anything. I can do that with any resource on the web, no?
>>
>> Adding the properties per se doesn't break anything, but when they are presented
>> as addressing a use-case that I don't believe can be addressed by RDF semantics,
>> they run the risk of encouraging people to creating RDF data that doesn't mean
>> what they think it means when interp[reted in accordance with RDF semantics.
>>
>> #g
>> --
>>
>>> Paul
>>>
>>> On Jun 27, 2012, at 19:09, Graham Klyne<graham.klyne@zoo.ox.ac.uk>  wrote:
>>>
>>>> On 27/06/2012 10:49, Luc Moreau wrote:
>>>>> All,
>>>>>
>>>>> At the face to face meeting, we have agreed to rename contextualization and mark
>>>>> this feature
>>>>> at risk. Tim, Stephan, Paul and I have worked a solution that we now share with
>>>>> the working group.
>>>>
>>>> I'm afraid I still have a problem with this.
>>>>
>>>> Considering your bundle tool:analysis01:
>>>> [[
>>>> bundle tool:analysis01
>>>>      agent(tool:Bob-2011-11-16, [perf:rating="good"])
>>>>      specializationOf(tool:Bob-2011-11-16, ex:Bob, ex:run1)
>>>>
>>>>      agent(tool:Bob-2011-11-17, [perf:rating="bad"])
>>>>      specializationOf(tool:Bob-2011-11-17, ex:Bob, ex:run2)
>>>> endBundle
>>>> ]]
>>>>
>>>> The problem is that, if subject to RDF semantics for URI interpretation, I can
>>>> see no semantic distinction is possible between
>>>>
>>>>    tool:Bob-2011-11-16
>>>> and
>>>>    tool:Bob-2011-11-17
>>>>
>>>> I.e. they are both specializations of ex:Bob, and that is all we can know about
>>>> them, as (by the nature of the semantics of URI interpretation) the denotation
>>>> of ex:Bob that appears in ex:run1 is the same as the denotation of ex:Bob that
>>>> appears in ex:run2.
>>>>
>>>> ...
>>>>
>>>> I do, however, have a different compromise that provides a hook for introducing
>>>> possible semantics later, or in private implementations, without sneaking in
>>>> something that could well turn out to be incompatible with, or just different
>>>> than, what the RDF group may do for semantics of datasets.
>>>>
>>>> The hook is this: simply allow attributes for the specializationOf relation, but
>>>> don't define a specific attribute for bundle.  This would allow you to do a
>>>> private implementation of the scheme you describe, but would not allow it to be
>>>> mistaken for something that has standardized semantics.  As in:
>>>>
>>>>    specializationOf(tool:Bob-2011-11-17, ex:Bob,
>>>>                     [myprivateattribute:bundle=ex:run2])
>>>>
>>>> ...
>>>>
>>>> In case you think I'm jumping at shadows here, I'll note that RDF has been here
>>>> before.  The original 1999 RDF specification described reification without
>>>> formal semantics.  Reification was intended to allow for capturing this kind of
>>>> information - i.e. to make assertions about context of use, etc - a kind of
>>>> proto-provenance, if you like.  But when the group came to define a formal
>>>> semantics for RDF, there were two possible, reasonable and semantically
>>>> incompatible approaches; looking at the way that reification was being used "in
>>>> the wild", it turned out that there was data out there that corresponded to both
>>>> of these (incompatible) approaches.  This was in the very early days of the
>>>> semantic web, so the harm done was quite limited.  I think a similar mistake
>>>> today would cause much greater harm.
>>>>
>>>> I think the appropriate way forward is to take this tool performance analysis
>>>> use-case to the RDF-PROV coordination group, and ask that it be considered as
>>>> input when defining semantics for RDF datasets.  I would expect that whatever
>>>> semantic structure they choose, it should be able to accommodate the use-case.
>>>> Then, we should be better placed to create an appropriate and compatible
>>>> contextualization semantics for provenance bundles.  But until then, I think we
>>>> invite problems by trying to create a standardized data model structure without
>>>> standardized RDF-compatible semantics to accommodate this use-case.
>>>>
>>>> #g
>>>> --
>>>>
>>>> Tracker, this is ISSUE-385
>>>>
>>>> On 27/06/2012 10:49, Luc Moreau wrote:
>>>>> All,
>>>>>
>>>>> At the face to face meeting, we have agreed to rename contextualization and mark
>>>>> this feature
>>>>> at risk. Tim, Stephan, Paul and I have worked a solution that we now share with
>>>>> the working group.
>>>>>
>>>>> Given that contextualization was already defined as a kind of specialization, we
>>>>> now allow an optional
>>>>> bundle argument in the specialization relation. (Hence, no need to create a new
>>>>> concept!)
>>>>>
>>>>> See section 5.5.1 in the current Editor's draft
>>>>> http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-dm.html#term-specialization
>>>>>
>>>>> Feedback welcome.
>>>>>
>>>>> Regards,
>>>>> Luc
>>>>>
>>>>> PS. Tracker, this is ISSUE-385
>>>>>
>>>>
>>>
>>>
>
>
Received on Thursday, 28 June 2012 08:46:09 UTC

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