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Re: PROV-ISSUE-1 (define-resource): Definition for concept 'Resource' [Provenance Terminology]

From: James Cheney <jcheney@inf.ed.ac.uk>
Date: Thu, 2 Jun 2011 12:41:17 +0100
Cc: Paolo Missier <Paolo.Missier@ncl.ac.uk>, "public-prov-wg@w3.org" <public-prov-wg@w3.org>
Message-Id: <10B72873-64C4-4152-87A0-27A60023AC8F@inf.ed.ac.uk>
To: Graham Klyne <GK@ninebynine.org>
('binary' encoding is not supported, stored as-is)
Yes, these issues seem intuitive only as long as you don't stop to  
think about them too hard :)

I would say that the provenance has to be scoped by (say) a start and  
end time, or some other criterion, to prevent the "big bang" problem  
(see e.g. [Miles IPAW 2006]).

If we want the provenance of the car from "now" until it was made,  
then the provenance of A needs to be included (e.g., maybe A caused  
damage to the car when it failed, so we need to know that to  
understand how the car's current state was obtained from its initial  
state).

If we want the provenance of the car from "now" until I bought it,  
which happened after the engine was replaced, then maybe I don't need  
to know about A.  (If I want to buy the car, I'd probably value the  
knowledge of the earlier history so that I can understand its current  
state, but the seller isn't always obligated to provide this.)

This reminds me of another good story:

The ship wherein Theseus and the youth of Athens returned [from Crete]  
had thirty oars, and was preserved by the Athenians down even to the  
time of Demetrius Phalereus, for they took away the old planks as they  
decayed, putting in new and stronger timber in their place, insomuch  
that this ship became a standing example among the philosophers, for  
the logical question of things that grow; one side holding that the  
ship remained the same, and the other contending that it was not the  
same.
—Plutarch, Theseus [http://en.wikipedia.org/wiki/Ship_of_Theseus]

What is the provenance of the ship?  Was the ship really "preserved"?

--James

On Jun 2, 2011, at 12:05 PM, Graham Klyne wrote:

> I think Paolo has usefully threaded a path through our discussions.   
> Thanks!  At first reading, I would consent (in the sense of  
> "consensus") to definitions framed on the basis of what he has  
> written here.
>
> ...
>
> The issue of monotonicity (of provenance of a stateful resource) is  
> interesting. Intuitively, it seems appropriate, but I'd need to let  
> it stew awhile before accepting it unconditionally.  My immediate  
> concern is how do we account for correction of previous errors in  
> provenance claims?  But this question goes to the heart of what is,  
> IMO, one of the key purposes of provenance on the Web (i.e. to help  
> deal with conflicting information in the Web, and the Semantic Web  
> in particular), so maybe that point gets addressed separately in any  
> case.
>
> Aha!  I just thought of another example:  suppose we're talking  
> about provenance of a car (e.g. for QA purposes).  Initially,  
> suppose it has engine A, made by a particular factory.  The  
> provenance of the car include the provenance of engine A.  Sometime  
> in its life, the engine fails and is replaced by engine B, and  
> provenance of engine C becomes part of the car's provenance.  At  
> this point, does it make sense to claim that the provenance of A is  
> still part of the car's provenance?  A similar example could be  
> constructed for, say, a photo album where images are added and  
> removed.
>
> #g
> --
>
>
> Paolo Missier wrote:
>> All
>> ok, so far I have been able to catch up with the Resource ISSUE 1,  
>> and believe me it took a while.  I have not digested anything else.
>> It seems that some consensus is emerging, so let me throw in my 2  
>> cents as a summary of my understanding +more questions, hoping not
>> to undo progress that has been made on this.
>> Summary:
>> =======
>> I seem to see a consensus that resources have, or can be given, an  
>> identity:
>>  >   - For our purposes, a resource is anything which can be  
>> referred to  (SM)
>> there is also a discussion on whether an Information Object has the  
>> same resource status as a resource as a physical object, but I
>> wouldn't be able to add to that discussion. To me, the objects that  
>> matter are primarily data structures,  documents, and
>> assertions, and I think what we are saying does apply to those.
>> I also agree with SM, GK, etc. that
>>  >   - When we talk about the provenance of a resource, we mean the
>>  >  provenance of its state on asking the question.
>> so we also agree that there is an implicit notion of resource state:
>> - resource state ->  r-snapshot   (LM)
>> and I personally agree that any notion of provenance refers to a  
>> specific state of a resource.  Naturally here we mean "observable
>> state". I have not seen the notion of observer introduced in this  
>> discussion (I have yet to catch up with the others!), but it seems
>> natural that provenance is relative to an observer.
>> - the fact that the Web architecture defines its foundational  
>> concepts similarly should be viewed as a convenience which will help
>> ground the concepts, rather than a set of constraints that we are  
>> bound to.
>> Additionally:
>> ========
>> - can we also assume that provenance is /monotonic/ wrt the state  
>> evolution of the resource it refers to.
>> This is desirable (for computational purposes) and seems to follow  
>> naturally from associating provenance to a state: let r_s be a
>> resource r in state s. Its provenance prov(r_s) is a subset of  
>> prov(r_{s'}) for any s' that temporally follows s. yes?
>> - Given a resource r in a state s: r_s, one can create one or more  
>> representations ("manifestations") repr(r_s) of r_s. These are
>> all r-snapshots or r_s.
>> - importantly, Jun writes:
>>  >  If f1 is a file, then it is a representation of a resource, not a
>>  >  resource any more, right?
>> I would argue that  repr(r_s) *should be a resource itself*, for  
>> any resource r and (visible) state s. Indeed, it has an initial
>> state (the time it is created from the underlying resource state),  
>> and its provenance at that state is simply the provenance of r_s,
>> plus the action of creating repr(r_s).   Then It can then evolve  
>> independently (but monotonically) as that new representation is
>> acted upon. The provenance of any further state, is prefixed by  
>> that just mentioned by monotonicity.
>> Containers:
>> ======
>> I do have a problem with "containers" as a separate notion from  
>> resource, however.
>> Isn't a database a container? and a resource? (it does have a  
>> state, which is the set of all its elements, and for a given state I
>> can certainly exhibit the provenance of each data item it contains).
>> So I am not sure the notion of container is useful here, or even  
>> well-founded:  you end up with issues of granularity, because
>> containers may be nested. But then anything non-atomic, like a  
>> tuple, is a container, which however does have a provenance, as we  
>> know.
>> Oh, well. Just more noise, perhaps.
>> Regards,
>>    -Paolo
>
>
>



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Received on Thursday, 2 June 2011 11:42:10 GMT

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