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

From: Simon Miles <simon.miles@kcl.ac.uk>
Date: Thu, 10 Nov 2011 14:58:36 +0000
Message-ID: <CAKc1nHcMV-hEj6wPs1kcf53tssgCiT_U4Dy5MS3U9m0wGnG8xQ@mail.gmail.com>
To: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Luc,

Yes, I think the analogy is correct. I claim that C2 is not
necessarily derived from e, because of the nature of the collection. I
cannot claim that it is never derived from e.

Being specific about the collection structure, maybe C0 is a tree, a
subtree e is added to make tree C1, then removed to make tree C2 (and
other changes might take place also). I claim that C2 was eventually
derived from C0 and from C1 but not e, as it wouldn't have made a
difference to C2 what subtree e contained or whether it had existed at
all. However, some might say it is odd to exclude e from C2's history
entirely as we don't know what would have occurred if e had not
existed, so we allow that C2 'depended on' e.

I'm sure there are structures where adding then removing an element
has an effect on the eventual collection (the eventual collection
would not be as it is had it not been for the element). If so, then
the eventual collection would be derived from the element.


On 10 November 2011 13:50, Luc Moreau <l.moreau@ecs.soton.ac.uk> wrote:
> Hi Simon,
> Still trying to understand what you wrote.
> Paraphrasing your example,
>  Someone asserts that a collection C2 is derived from collection C1 by
> removing e from C1
>  You claim that C2 is not necessarily derived from e,
>   or
>  do you claim that C2 is never derived from e,
> Is it a correct analogy?  which claim are you making?
> Thanks,
> Luc
> On 10/11/2011 10:46, Simon Miles wrote:
>> In my example, the designer may assert that the first draft page was
>> derived from the banner image ("DRAFT") that it contains, while the
>> publisher may assert that the published page (excluding the banner)
>> was derived from the first draft. But the published page is not
>> derived from the banner image, because it would not make any
>> difference should the banner have been different, or even not been
>> present at all, e.g. the first draft could still have existed even if
>> the banner had been deleted earlier. To allow a transitive
>> derivation-like relation to exist, it must have semantics so weak as
>> to allow the published page to be linked to the banner. I understood
>> this weakened relation to be dependedOn. This relation does not remove
>> the need for an actual derivation relation to be expressed. I don't
>> have a strong opinion on whether a transitive relation needs to exist.

Dr Simon Miles
Lecturer, Department of Informatics
Kings College London, WC2R 2LS, UK
+44 (0)20 7848 1166
Received on Thursday, 10 November 2011 14:59:04 UTC

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