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Re: writing a simple example in prov-o, help

From: Luc Moreau <l.moreau@ecs.soton.ac.uk>
Date: Wed, 26 Oct 2011 22:01:38 +0100
Message-ID: <EMEW3|f9af457900f657d37892a0f1887c83f2n9PM1g08l.moreau|ecs.soton.ac.uk|4EA87532.3050100@ecs.soton.ac.uk>
To: Simon Miles <simon.miles@kcl.ac.uk>
CC: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Simon,
Not sure which document it should go in, but it would definitely be worth
writing this up!
Luc

On 26/10/2011 18:45, Simon Miles wrote:
> Hi Luc,
>
> Wouldn't it be more appropriate in deliverable D6 (best practice
> cookbook) to describe topics such as how to be robust to changes? It
> could be in the primer, but we'd need to separate the gentle
> introduction to how to use the model (which I would see as the
> primer's main role) from the consideration of nuanced situations.
> These could be distinct parts of the document.
>
> Thanks,
> Simon
>
> On 26 October 2011 15:50, Luc Moreau<L.Moreau@ecs.soton.ac.uk>  wrote:
>    
>> Hi Simon and Paul,
>>
>> I see this simple example as good because it shows us that
>> we don't have to write much to express provenance.
>> Better some, than none!
>>
>> As always, this comes with some limitations, and I would
>> see the role of the primer to discuss potential issues with these
>> assertions as the world changes (e.g. video content changes).
>> BTW, that's not typical of provenance, but it's typical of any metadata.
>>
>> The primer could discuss ways of making the assertions more
>> robust to changes.  A range of option exists, but they have to be discussed:
>> - cool uris are really OK only for the publisher
>> - adding the time at which
>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>
>>     was used would make those statements much stronger
>> - adding further characterization, e.g. hash of the video, etc.
>>
>> Luc
>>
>> On 10/26/2011 10:53 AM, Simon Miles wrote:
>>      
>>> Hi Paul,
>>>
>>> I think the argument you make is the same as implied by my example...
>>> except that the conclusion is different.
>>>
>>> As you say, the provenance best practice could be to use permalinks.
>>> So, in the example, the bloggers should use permalinks. They have no
>>> control over what the original YouTube URL deferences to, so cannot
>>> ensure it is a permalink. Unless they have special information, they
>>> can only assume it is not, and so either they:
>>>     (a) cannot say anything about the video at all, or
>>>     (b) need to create their own permalink to refer to the video.
>>> If doing (b), this new URI clearly should connect to the YouTube URL
>>> as it is the video that the provenance is about. However, to make it
>>> into a permalink, there must be something more which ensures it always
>>> describes the same content, i.e. characterisation of the entity. The
>>> provenance then looks like the PROV-OM examples rather than the simple
>>> link.
>>>
>>> I'm not clear if you are arguing for option (a) in your email, i.e.
>>> limit people to only refer to things in their provenance when they can
>>> control those thing's immutability, but this seems very restrictive.
>>>
>>> I'm not saying I prefer the long-winded provenance data, just that it
>>> appears the desire for interoperability makes it necessary beyond
>>> limited cases.
>>>
>>> I think accounts and consistency are tangential issues - there is
>>> nothing inconsistent in what is asserted, the inconsistency comes only
>>> from the ambiguity of what is being asserted about.
>>>
>>> Thanks,
>>> Simon
>>>
>>>
>>>        
>>>> The point is that two different people are asserting it. We can't
>>>> maintain consistency across the people. This is why we have accounts, no?
>>>>
>>>> I think one way to handle this is to have a best practice where we
>>>> suggest people use permalinks (see
>>>> http://en.wikipedia.org/wiki/Permalink) or cool-uris.  Indeed, to me
>>>> this is probably the best way to introduce entities.
>>>>
>>>> So overall, my suggestion would be to maintain simplicity but suggest
>>>> people use uris that refer to content that doesn't change.
>>>>
>>>> But please bring this up in interoperability page.
>>>>
>>>> cheers,
>>>> Paul
>>>>
>>>>
>>>>
>>>> Simon Miles wrote:
>>>>
>>>>          
>>>>> Paul, all,
>>>>>
>>>>> Just to properly understand why what is being discussed is important,
>>>>> I wanted to expand your example to a larger use case.
>>>>>
>>>>> At time T, you say something about a video on your blog and assert:
>>>>> <http://thinklinks.wordpress.com/2011/07/31/why-provenance-is-fundamental-for-people/>
>>>>> prov:wasDerivedFrom
>>>>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.
>>>>>
>>>>> At time T+1, the video is edited to introduce a previously missing
>>>>> segment that undermines the message of your blog entry. The video URI
>>>>> stays the same.
>>>>>
>>>>> At time T+2, I say something about the (updated) video on my blog and assert:
>>>>> <http://inkings.org/2011/10/08/why-provenance-is-pointless/>
>>>>> prov:wasDerivedFrom
>>>>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.
>>>>>
>>>>> We could then observe:
>>>>>     - Even if the above use case doesn't happen to you, by using the
>>>>> simplest form of provenance you are opening the possibility of it
>>>>> happening and you would not even know about it.
>>>>>     - It doesn't help to say that the video owners shouldn't use the same
>>>>> URL, because it is not under the control of either those creating or
>>>>> consuming the provenance.
>>>>>     - There is nothing apparently wrong with either of our assertions
>>>>> (except the lack of characterisation), and I don't know anything about
>>>>> your blog so don't take it into account in my blog's provenance.
>>>>>     - It seems reasonable criteria for interoperability that if you read
>>>>> Prov-DM from two separate sources referring to the same entity, then
>>>>> either there is an error in (at least) one or they are mutually
>>>>> consistent. I couldn't see what this would correspond to in the
>>>>> interoperability discussion [1] though.
>>>>>
>>>>> Thanks,
>>>>> Simon
>>>>>
>>>>> [1] http://www.w3.org/2011/prov/wiki/Interoperability
>>>>>
>>>>>
>>>>>            
>>>>
>>>>
>>>>          
>>>
>>>
>>>        
>> --
>> Professor Luc Moreau
>> Electronics and Computer Science   tel:   +44 23 8059 4487
>> University of Southampton          fax:   +44 23 8059 2865
>> Southampton SO17 1BJ               email: l.moreau@ecs.soton.ac.uk
>> United Kingdom                     http://www.ecs.soton.ac.uk/~lavm
>>
>>
>>
>>      
>
>
>    
Received on Wednesday, 26 October 2011 21:02:22 GMT

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