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Re: Dictionary/Collection: where are we?

From: Paul Groth <p.t.groth@vu.nl>
Date: Thu, 7 Jun 2012 11:53:18 +0200
Message-ID: <CAJCyKRqQx5n+rx=6eRaLYSO774iG2d2O-rcEsO7hXsot_kXWmQ@mail.gmail.com>
To: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Cc: Provenance Working Group WG <public-prov-wg@w3.org>
Added to the agenda.

Thanks
Paul

On Thu, Jun 7, 2012 at 9:59 AM, Luc Moreau <L.Moreau@ecs.soton.ac.uk> wrote:
> Dear all,
>
> We have had multiple threads discussing collections lately.
> I would like to summarise what collections currently are in prov-dm, and
> check whether it's still what people want.
>
> 1. A notion of EmptyDictionary:  it's complete knowledge, no future
> knowledge can change its empty nature
>
> 2. A relation insertion that completely list pairs to be added to a
> dictionary, with an update semantics.
>
> 3 A relation removal that completely lists keys of pairs to be removed
> from the dictionary
>
> 4. The property that the state of a dictionary is computable: given a
> complete knowledge of a dictionary, any sequence of insertion/removal
> leads to a dictionary whose state can exactly be computed.
>
> 5. Incomplete knowledge of a dictionary state can be modelled  by not
> specifying the initial state of a dictionary (see d1,d2 in example
> http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-dm.html#example_53)
> or by introducing derivations (see c2 in example
> http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-constraints.html#collections-and-derivation)
>
> 6 so far, no mention of membership relation!
>   So, if there are issues regarding CWA, they need to be discussed for
> the above.
>
> 7. Membership defined, in this context, as a convenience notation for an
> insertion operation into an unspecified dictionary.
> See  constraint 38 in prov-constraints
> (http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-constraints.html#membership-as-insertion).
>
> 8. Complete membership defined, in this context, as a convenience
> notation for an insertion operation into an empty dictionary.
>
> 9. There was a request to disallow complete membership. Given that this
> is just a convenience notation, it's unclear why we do this? 1, 2, 3, 4
> are all about complete knowledge of a dictionary state.
>
> 10. Prov-dm define a type prov:collection but NO relation that applies
> to it.
>
> 11 a further point was discussed: can we specify a membership relation
> for collections. given point 4 above, the axiomatisation of dictionary
> requires comparison of its members. It's ok for dictionaries, since we
> compare keys. It's unclear how we can make this compatible with a
> membership for a collection of entities.
>
> Where does it leave us?
>
> 1. Do we want to allow dictionaries for which we have complete knowledge
> of the contents?
> 1.1 if yes, what's the point of removing the complete flag
> 1.2 if no, .... Go back to drawing board for dictionaries ....
>      ... Realistically, that looks like the final nail ...
>
> 2. If we have specified dictionaries and their relations, then do we
> need to specify some relations for collections?
>
> --
> 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
>
>



-- 
--
Dr. Paul Groth (p.t.groth@vu.nl)
http://www.few.vu.nl/~pgroth/
Assistant Professor
Knowledge Representation & Reasoning Group
Artificial Intelligence Section
Department of Computer Science
VU University Amsterdam
Received on Thursday, 7 June 2012 09:53:52 UTC

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