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Re: PROV-ISSUE-7 (define-derivation): Definition for Concept 'Derivation' [Provenance Terminology]

From: Graham Klyne <GK@ninebynine.org>
Date: Thu, 02 Jun 2011 20:45:59 +0100
Message-ID: <4DE7E877.3060709@ninebynine.org>
To: Khalid Belhajjame <Khalid.Belhajjame@cs.man.ac.uk>
CC: Luc Moreau <L.Moreau@ecs.soton.ac.uk>, public-prov-wg@w3.org
Khalid Belhajjame wrote:
> 
> Hi Graham,
> 
>  >I agree that many of the examples of derivation we have raised relate 
> to resource states.  But if, as has been suggested by myself and others, 
> resource states are themselves resources >(especially when named for the 
> purposes of expressing a derivation), then such derivations can equally 
> be regarded as relating resources.  I think that's more a difference of 
> terminology than >fundamental.
> 
> Would it be fair then to say that in that view resources are immutable 
> resources?

In the case of resources representing a snapshot of state, yes.

> Which bring me to the question, do we want to express derivations 
> between mutable resources, or that is just something that we should 
> avoid at this point?

(I'm finishing this email after today's telecon, so it's a bit of a re-run.)

I think that many of our use-cases are based on invariant values, and the 
near-term goal is to find expression for these.  So we definitely do want to 
express derivations between non-varying values.  But in so doing, it's not clear 
to me (yet) that we need to exclude mutable resources, so I say let's keep our 
options open and not close off any possibilities that we don't have to.

So my answer to avoiding mutable resources is: "yes and no".

#g
--


> 
> Thanks, khalid
> 
>>
>> Where I think I may diverge from what you say is that I would not 
>> limit such expressions of derivation to resources that happen to be a 
>> state (or snapshot of state) of some resource.  I think defining that 
>> distinction in a hard-and-fast way, that also aligns with various 
>> intuitions we may have about derivation, may prove difficult to 
>> achieve (e.g. as I think is suggested by Jim Meyers in 
>> http://lists.w3.org/Archives/Public/public-prov-wg/2011Jun/0015.html 
>> (*)).
>>
>> #g
>> -- 
>>
>> (*) I just love the W3C mailing list archives - so easy to find links 
>> to messages, and thus capture provenance!
>>
>> Khalid Belhajjame wrote:
>>>
>>> Hi,
>>>
>>>  From the discussion so far on derivation it seems that most people 
>>> tend to define derivation between resource states or resources state 
>>> representations, but not for resources.
>>>
>>> My take on this is that in a context where a resource is mutable, 
>>> derivations will mainly be used to associate resource states and 
>>> resource states representations.
>>>
>>> That said, based on derivations connecting resource states and 
>>> resources state representations, one can infer new derivations 
>>> between resources. For example, consider the resource r_1 and the 
>>> associated resource state r_1_s, and consider that r_1_s was used to 
>>> construct a new resource state r_2_s, actually the first state, of 
>>> the resource r2. We can state that r_2_s is derived from r_1_s, i.e., 
>>> r_1_s -> r_2_s. We can also state that the resource r_2 is derived 
>>> from the resource r_1, i.e., r_1 -> r_2
>>>
>>> PS: I added a defintiion of derivation within this lines to the wiki:
>>> http://www.w3.org/2011/prov/wiki/ConceptDerivation
>>>
>>> Thanks, khalid
>>>
>>>
>>>
>>>
>>> On 01/06/2011 07:49, Luc Moreau wrote:
>>>> Hi Graham,
>>>>
>>>> Isn't it that you used the duri scheme to name the two resource 
>>>> states that exist in
>>>> this scenario?
>>>>
>>>> In your view of the web, is there a notion of stateful resource? 
>>>> Does it apply here?
>>>>
>>>> Thanks,
>>>> Luc
>>>>
>>>>
>>>>
>>>> On 31/05/11 23:57, Graham Klyne wrote:
>>>>> Luc Moreau wrote:
>>>>>> Graham,
>>>>>>
>>>>>> In my example, I really mean for the two versions of the chart to 
>>>>>> be available at
>>>>>> the same URI. (So, definitely, an uncool URI!)
>>>>>>
>>>>>> In that case, there is a *single* resource, but it is stateful. 
>>>>>> Hence, there
>>>>>> are two *resource states*, one generated using (stats2), and the 
>>>>>> other using (stats3).
>>>>>
>>>>> Luc,
>>>>>
>>>>> I had interpreted your scenario as using a common URI as you explain.
>>>>>
>>>>> But there are still several resources here, but they are not all 
>>>>> exposed on the web or assigned URIs.  I'm appealing here to 
>>>>> anything that *might* be identified as opposed to things that 
>>>>> actually are assigned URIs.   (For example, the proposed duri: 
>>>>> scheme might be used - 
>>>>> http://tools.ietf.org/id/draft-masinter-dated-uri-07.html)
>>>>>
>>>>> (And the URI is perfectly "cool" if it is specifically intended to 
>>>>> denote a dynamic resource.  A URI used to access the current 
>>>>> weather in London can be stable if properly managed.)
>>>>>
>>>>> (I think this is all entirely consistent with my earlier stated 
>>>>> positions.)
>>>>>
>>>>> #g
>>>>> -- 
>>>>>
>>>>>> Of course, if blogger had used cool uris, then, c2s2 and c2s3 
>>>>>> would be different resources.
>>>>>>
>>>>>> Luc
>>>>>>
>>>>>> On 05/31/2011 02:25 PM, Graham Klyne wrote:
>>>>>>> I see (at least) two resources associated with (c2):  one 
>>>>>>> generated using (stats2), and other using (stats3).  We might 
>>>>>>> call these (c2s2) and (c2s3). 
>>>>>>
>>>>
>>>>
>>>
>>
>>
> 
> 
Received on Thursday, 2 June 2011 21:15:56 GMT

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