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Re: Changes to prov:Dictionary

From: Timothy Lebo <lebot@rpi.edu>
Date: Thu, 7 Jun 2012 07:52:10 -0400
Cc: Stephan Zednik <zednis@rpi.edu>, Luc Moreau <L.Moreau@ecs.soton.ac.uk>, "public-prov-wg@w3.org WG" <public-prov-wg@w3.org>
Message-Id: <2EB3AF3B-F256-45DF-B418-0846CC52FDCC@rpi.edu>
To: Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk>

On Jun 7, 2012, at 5:40 AM, Stian Soiland-Reyes wrote:

> On Wed, Jun 6, 2012 at 5:03 PM, Stephan Zednik <zednis@rpi.edu> wrote:
>> Are you specifically worried about the possibility that other members may be
>> asserted at a later time by someone else?  If this is an issue than perhaps
>> you could use a system-specific extension of prov:Collection which utilizes
>> a terminated ordered list.
> I am not worried about this. I would consider a provenance account
> initially in isolation, just like I would consider a textual log file
> in isolation. Integrating provenance statements from various sources
> might or might not give an inconsistent picture.
> I'm worried that if I receive a provenance trace which describes the
> members of a collection, then I don't know if these are just some of
> the members or if they are all of the members, as the PROV standard
> does not distinguish between the two. Perhaps that is a domain
> specific problem, but I believed it would be rather general
> requirement for a data structure like a Dictionary.
> For my particular use case, I would be using incomplete membership for
> the provenance of a workflow run that it is ongoing or cancelled, and
> a complete membership once the engine can tell me a collection has
> been completed (iteration finished) when we know for sure there is
> nothing more.  This can obviously also be asserted by terminating the
> iteration activity, so it's not a strong requirement for me - it just
> seem like a source of disambiguousness.

FWIW, my supreme court example could benefit from this disambiguation.
As I asserted it, I knew that I listed them all. But nothing in there is conveying my knowledge of that.
If I had committed that file every 30 seconds while I was editing, the one, then two, then three members that 
I dug up and wrote down would have been an incomplete collection.

Perhaps we can avoid the OWA dragon and just look at what the asserter is saying, and wants to say.
prov:CompleteDictionary isn't a promise of "you'll never find any more from anywhere"; instead it's a promise that "you'll never find any more members _from me_".

I think that could be the distinction that strikes the compromise.

>> I must reiterate my agreement with Graham's point above that this need from
>> this use case should not become a requirement for all collections defined in
>> the standard.
> I can agree if the group believes that dictionaries can still
> generally be useful without knowing that it is complete or not (I
> personally doubt this). The examples I have seen so far seem to assume
> completeness, like members of the US Supreme Court (we know seat 5 and
> 7 are empty in :todays-us-supreme-court but can't state that without
> completion).


> No attribute or class specialization will resolve the issue of trying to
>> enforce CWA in RDF.
> That's not strictly true. For instance if you claim that a dictionary
> is a prov:EmptyDictionary, then it can't also have members without
> making the provenance account inconsistent. (OWL does not enforce this
> now, as it would require adding disjointness to prov:EmptyDictionary
> to the domain of prov:memberOf, which is out of RL)

We could add this if it's fundamental. It would just involve another entry into 

>> I think in general the idea of 'completeness' is incompatible with OWA and
>> should not be addressed in PROV-O.
> Even with RDF Lists? Or would you consider that feature creep? I can
> bend to that to finish the debate. :)

Noooo! Uncle! Uncle!
Have your prov:CompleteDictionary, just stop waving that rdf:LIst around.

I think if we make this not about OWA, but a means to permit an assertion from an asserter about his situation, "completeness" can be just fine.


> -- 
> Stian Soiland-Reyes, myGrid team
> School of Computer Science
> The University of Manchester
Received on Thursday, 7 June 2012 11:54:11 UTC

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