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RE: PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually "IVP of" each other [Conceptual Model]

From: Cresswell, Stephen <stephen.cresswell@tso.co.uk>
Date: Tue, 27 Sep 2011 12:48:14 +0100
Message-ID: <F22D0BFCDD4DDC44B92C4E24D751CB938D76FF@W3EXC017023.theso.co.uk>
To: "Luc Moreau" <L.Moreau@ecs.soton.ac.uk>, <public-prov-wg@w3.org>
Hi Luc,

 

> I don't understand this idea of "defining a new entity" (your point
(1)).

> Where is this coming from?

 

It's coming from the PROV data model document, where
wasComplementOf-necessary-cond says 'An assertion "wasComplementOf(B,A)"
holds over the temporal intersection of A and B, only if:...'

 

It's also coming from Paolo's explanation of the intention behind
complementOf (
http://lists.w3.org/Archives/Public/public-prov-wg/2011Aug/0048.html ).

"To the extent that two BOBs provide two perspective on an entity, both
of which are partial, the intent is to establish a correspondence so
that it makes sense to take the union (modulo some mapping) of the two
sets of attributes. This reults in more complete knowledge about the
entity within a certain time interval."

 

So wasComplementOf(B,A) implicitly introduces both a time interval and a
set of attributes.  Surely that's an entity.

 

> Looking back at the definition we had reached by the time of F2F [1],
I don't see this entity being

mentioned.

 

I was not saying that using of the original IVPof introduced an implicit
new entity.  I meant that a symmetric variant of wasComplementOf(B,A)
assertion could be made by introducing an explicit entity C to represent
the overlap of A and B, and then making two assertions IVPof(C,A) and
IVPof(C,B).

 

Whether that works depends on the exact definition of IVPof.  The IVPof
from the time of F2F1 does not say anything about time intervals (it
wasn't made clear until after F2F1 that a bob/entity is associated with
a continuous time interval).  It is my intuitive understanding that an
"invariant view" or "contextually constrained form" of an entity has a
time interval which is within that of the viewed entity.  I may be on my
own there, but I did qualify that I was using that variant in my earlier
email.  I realise that probably the first time the official definition
of IVPof said anything about time, it was in the current
"wasComplementOf" form, which is about overlap and rather than inclusion
of time intervals.  I think that temporal inclusion is a really useful
to be able to assert, and that the model ought to let us do that.

 

Stephen Cresswell

Tel:  +44 (0) 01603 69 6926

Web:  www.tso.co.uk <http://www.tso.co.uk/> 

 

________________________________

From: public-prov-wg-request@w3.org
[mailto:public-prov-wg-request@w3.org] On Behalf Of Luc Moreau
Sent: 26 September 2011 09:57
To: public-prov-wg@w3.org
Subject: Re: PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually
"IVP of" each other [Conceptual Model]

 

Hi Stephen,

I don't understand this idea of "defining a new entity" (your point
(1)).
Where is this coming from?

Given that entity expressions are asserted by asserters, and therefore,
their specific attributes
selected by asserters, why would we have an entity with attribute-value
pairs formed by
the union of those of A and B?  While I can see we can do it
mathematically, why would such
an entity expression make sense from a practical view point (when A and
B may be radically
different perspectives over the same thing).

Looking back at the definition we had reached by the time of F2F [1], I
don't see this entity being
mentioned.

Cheers,
Luc

[1] http://www.w3.org/2011/prov/wiki/F2F1ConceptDefinitions#IVP_of


On 09/25/2011 10:03 PM, Cresswell, Stephen wrote: 

 

Jim Myers wrote:
> I'm not sure what of 29 and 57 then survive as unresolved concerns -
perhaps whether transitivity can be defined?

I have two concerns (or perhaps the same concern approached from two
directions).

(1)
I think that the assertion wasComplementOf(B,A) implicitly defines a new
entity.
The new entity has a time interval which is the temporal intersection of
those of A and B.
The new entity has a set of attribute-value pairs which is the union of
those of A and B.

However, if I want to make this new entity explicit, I can't.  The
vocabulary I need to use to state its relationship to A and B is
missing.


(2)
One use for the original IVPof was (I thought) to relate together
long-term entities (e.g. Luc-over-his-lifetime) with shorter-term
entities describing states (e.g. Luc-in-Boston).  Now it seems that the
strongest assertion that I can make about the relationship of these two
entities is:

  wasComplementOf( Luc-in-Boston, Luc-over-his-lifetime )

... but this just asserts that Luc's visit to Boston *overlapped* with
his lifetime, which is weaker than what I wanted to assert.

If I also want to describe a visit to MIT that Luc made while in Boston,
I could also assert

  wasComplementOf( Luc-at-MIT, Luc-in-Boston )

Since the assertions are quite vague, we can't infer that
Luc-over-his-lifetime contained Luc-at-MIT, and we can't even infer that
they overlapped.
I think it would be useful to be able to make some stronger assertions
that allow transitivity to be used here.  At some point during its
evolution, IVPof was close to being that helpful transitive relation,
but now its gone.  I think we still need it.

Stephen Cresswell

-----Original Message-----
From: Myers, Jim [mailto:MYERSJ4@rpi.edu]
Sent: Fri 23/09/2011 18:21
To: Cresswell, Stephen; Paolo Missier; public-prov-wg@w3.org
Subject: RE: PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually
"IVP  of"  each other  [Conceptual Model]

When I read the current document, I see complementOF is defined as
one-way - you can assert it in both directions, but the text talks about
a case where B is a complementOf A but not the reverse. Can the editors
confirm that's the intent? If so, perhaps we can move to refining text
to avoid the perception that symmetry is required (i.e. talk about the
asymmetric case first...). I'm not sure what of 29 and 57 then survive
as unresolved concerns - perhaps whether transitivity can be defined?

Cheers,
 Jim

> -----Original Message-----
> From: public-prov-wg-request@w3.org [mailto:public-prov-wg-
> request@w3.org] On Behalf Of Cresswell, Stephen
> Sent: Friday, September 23, 2011 10:15 AM
> To: Paolo Missier; public-prov-wg@w3.org
> Subject: RE: PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually
"IVP
> of" each other [Conceptual Model]
>
>
> Hi Paolo,
>
> Yes, I agree that the current wasComplementOf can be symmetrical, and
I
> have no objection to closing issue 29.
>
> I do still think that a concept of IVPof that is antisymmetric and
transitive, so
> that "B IVPof A" means something like "B and A describe the same
stuff,
> and B's interval is within A's interval" is a simpler and stronger
concept.  It
> can co-exist with wasComplementOf, and it can be used to define (a
> symmetric form of) wasComplementOf (which admittedly doesn't match
> the current definition).
> i.e.
>   (B wasComplementOf A) <=> exists C.(C IVPof A & C IVPof B)
>
> Since wasComplementOf is a relation that only holds over the temporal
> intersection A and B anyway, then saying it with this IVPof at least
makes
> you introduce an entity C that models the relevant interval.
>
> However, I think that's basically what Graham said and it is a
different issue
> - PROV-ISSUE-57.
>
> Stephen Cresswell
>
> Tel:  +44 (0) 01603 69 6926
>
> Web:  www.tso.co.uk
>
>
>
>
> -----Original Message-----
> From: public-prov-wg-request@w3.org
> [mailto:public-prov-wg-request@w3.org] On Behalf Of Paolo Missier
> Sent: 23 September 2011 12:06
> To: public-prov-wg@w3.org
> Subject: Re: PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually
"IVP
> of" each other [Conceptual Model]
>
> Hi,
>
> as we are going through older issues, this one seems to have been
> superseded by the current version of the model. We propose to close it
> pending review (that means, Stephen can you please call in with your
> current view on this, thank you).
>
> Specifically:  IVP-of has been replaced by ComplementOf, which *does*
> allow for symmetry.
>
> -Paolo
>
>
> On 7/11/11 12:22 PM, Provenance Working Group Issue Tracker wrote:
> > PROV-ISSUE-29 (mutual-iVP-of): can two bobs be mutually "IVP of"
each
> other  [Conceptual Model]
> >
> > http://www.w3.org/2011/prov/track/issues/29
> >
> > Raised by: Stephen Cresswell
> > On product: Conceptual Model
> >
> >
> > As it currently stands, I believe that it does not exclude the
> possibility that two bobs may be mutually "IVP of" each other -
> > i.e. you could have bobs A, B such that (B IVPof A)&  (A IVPof B),
and
> this is surely not intended.
> >
> > This could arise if, for bobs A, B :
> > - A and B both represent the same entity
> > - A and B share some immutable properties, and they have
corresponding
> values.
> > - B has some immutable properties which correspond to mutable
> properties of A
> > - A has some immutable properties which correspond to mutable
> properties of B
> >
> > Possibly the asserter-defined test (included in "IPV of" definition)
> that real world states modelled by A and B are "consistent" may
disallow
> > "IPV of" in this situation.  However, unless that is guaranteed, I
> think that the definition of "B IPV of A" (if it is still to have a
> definition) should additionally require that:
> > "A has no immutable properties which correspond to mutable
properties
> of B"
> >
> > Stephen
> >
> >
> >
> >
>
>
> --
> -----------  ~oo~  --------------
> Paolo Missier - Paolo.Missier@newcastle.ac.uk, pmissier@acm.org School
> of Computing Science, Newcastle University,  UK
> http://www.cs.ncl.ac.uk/people/Paolo.Missier
>
>
>
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-- 
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


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Received on Tuesday, 27 September 2011 11:48:48 GMT

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