W3C home > Mailing lists > Public > public-prov-wg@w3.org > November 2011

Re: prov-dm derivation: three proposals to vote on (deadline Wednesday midnight GMT)

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Wed, 09 Nov 2011 21:43:03 +0000
Message-ID: <EMEW3|7ee9e70b5baa17767c0dc870bd82a4fcnA8LhE08L.Moreau|ecs.soton.ac.uk|4EBAF3E7.9000308@ecs.soton.ac.uk>
To: public-prov-wg@w3.org
Hi again,

There was a consensus in the group that we wanted a transitive 
derivation relation,
and that's why dependedOn was defined to be transitive.

With the current prov-dm, we would be able to infer 
dependedOn(webpage,pencil).

You are arguing here, it's not the case. So, something is definitely broken.
So, this may question the existence of dependedOn.

Of course, maybe your example is misleading.

   wasEventuallyDerivedFrom(webpage, sketch1)
   wasEventuallyDerivedFrom(sketch, pencil)

I would argue that there are two sketches, one conceptual leading
to the webpage, the other physical, created with the pen. And yes
one is complement of the other!

So, this may not be a good counter for the non-transitivity of 
wasEventuallyDerivedFrom.
Can you find another example where transitivity does not work for 
wasEventuallyDerivedFrom?

Further comment interleaved.


On 09/11/11 21:01, Simon Miles wrote:
> Hi Luc,
>
>    
>> I don't see why wasEventuallyDericedFrom can't be transitive?
>>      
> Do you mean an instance or in general? If you mean in general, then
> for example, the webpage in the example was derived from the sketch,
> which was a pencil drawing on a sheet of paper. The sketch then was
> derived from the pencil. But the webpage was not derived from the
> pencil, as it would have been the same if the sketch was written in
> pen.
>
>    
>> It's also unclear how you decide between wasEventuallyDericed and dependendOn?
>>      
> I'm not sure the kind of decision procedure you're looking for, but I
> might go for:
>
> A wasEventuallyDerivedFrom B if B being different would have meant A
> was different.
> If B was used in a process that generated an entity, C, and A
> wasEventuallyDerivedFrom C or A dependedOn C, then A dependedOn B.
>
>    

I don't see how what you suggest can work:

used(p,B)
wasGeneratedBy(C,p)
wasEventuallyDerivedFrom(A,C)

B could be used by p after C was generated.  How can you derive
a dependency between A and B?

Let me repharse my question, I didn't understand in your example of
the webpage why you decided to choose dependedOn or wasEventuallyDerived.
It felt to me that you could have swapped them, and it would have still been
OK.

Luc

> Thanks,
> Simon
>
>    
>> Professor Luc Moreau
>> Electronics and Computer Science
>> University of Southampton
>> Southampton SO17 1BJ
>> United Kingdom
>>
>> On 9 Nov 2011, at 20:06, "Simon Miles"<simon.miles@kcl.ac.uk>  wrote:
>>
>>      
>>> If you think that we need a non-transitive relation wasEventuallyDerivedFrom, can you explain why?
>>>        
>>
>>      
>
>
>    
Received on Wednesday, 9 November 2011 21:43:44 UTC

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