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Re: prov-issue-11: what is version?

From: Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk>
Date: Wed, 29 Jun 2011 00:19:21 +0100
Message-ID: <BANLkTik-5naTBzOxxGyqWR0azex0NYb5qw@mail.gmail.com>
To: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Cc: public-prov-wg@w3.org
On Tue, Jun 28, 2011 at 17:03, Luc Moreau <L.Moreau@ecs.soton.ac.uk> wrote:

> If we agree with the definition I suggested (possible Jim's too, I am not
> sure), it shows that version (or is revision of) is not a primitive
> notion in PIL, but can be derived from more primitive concepts.
> I think we still need to take a view on this concept, since it is part of
> the charter,
> and we can't simply ignore it.

I like your definition, and I still think there could be room for the
concept, even if is just a composition of other concepts. I would also
call it 'revision' instead, because 'version' suggests a parent-child
relationship rather than a sibling one.

For reference:

> A thing B is a version of (or should we say revision of) a thing A if:
> * B is derived from A
> there exists a thing C, such that:
> * B is IVP of C
> * A is IVP of C
> * statements about C are optional

In particular because revisions can be done in many ways, and people
could disagree about whether B is a revision of A or not (by which
authority, etc), it would be a very useful thing for an asserter to
say that "I think B is a revision of A" - and to do that without
defining the abstract C which could be cumbersome and lead to
conflicts about my C (not) being the same as your C.

A Revision can also have additional properties, such as what/who
generated it (which might be different from who made the revised
thing). For our journalist example, Bob can assert that chart c2 is a
revision of chart c1 - while the newspaper don't want to do make such
a strong statement even if they (later) want to acknowledge the
existence of c2.

Uh oh - digression follows: I just realised that here c2 is *not* a
revision of c1, even for bob.

c2 is derived from f2
f2 is derived from d2
d2 is derived from d1
d1,d2 are IVPs of 'd0'

so only d2 is a revision of d1. f2 is not a revision of f1 by your
definition, and neither is c2 a revision of c1 - but I feel that they
probably should be.

If Bob explicitly says that c2 is a revision of c1 - then he's
implicitly saying that there's a common IVP of both c1 and c2. Is that
'd0', some kind of transitivity through f1/f2, r1/r2 etc, or just some
abstract idea about the "chart of d"?

Stian Soiland-Reyes, myGrid team
School of Computer Science
The University of Manchester
Received on Tuesday, 28 June 2011 23:20:20 UTC

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