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Re: Models and their use

From: Graham Klyne <GK@ninebynine.org>
Date: Thu, 14 Jul 2011 07:40:31 +0100
Message-ID: <4E1E8F5F.6090206@ninebynine.org>
To: "Myers, Jim" <MYERSJ4@rpi.edu>
CC: Simon Miles <simon.miles@kcl.ac.uk>, Provenance Working Group WG <public-prov-wg@w3.org>
Myers, Jim wrote:
> I'm having a hard time understanding how this discussion changes the model (or what version/interpretation of the model).

A trite response might be that, lacking a model, it changes nothing.

But I suspect that what is happening here is, lacking a common model at this 
stage, that we each have our own model which we are using to interpret or think 
about the terms we're trying to describe.

> Leaving out description, which I agree is separable, where do we stand with thing/IVP?

Well, I thought Simon's proposal [1] captured that part quite nicely.

(The term "entity" for was agreed at F2F1 [2] - I always thought that "thing" 
was just another term for entity, but checking the log at [2] I see this is not 
universally held - I never really tuned in to the distinction here.)

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

[2] http://www.w3.org/2011/prov/meeting/2011-07-06#Session_2__3a__Model_Task_Force


> Thing is being talked about as entity now (and was Bob for a while)? 

I think "bob" was never entirely clear - and may well have been the subject of 
multiple interpretations.  I for one am not comfortable with the notion of a 
"state" that "bob"

> And the argument is that we don't need to distinguish between the idea of a provenance
> thing and the entity definitions in other ontologies, or perhaps better - the mapping
 > of instances of the classes 'comet' and 'comet-near-star' to provenance 
entities is not
 > part of the model, but is an implementation detail?

There are several issues in this.  Let me try to pick apart:

"we don't need to distinguish between the idea of a provenance thing and the 
entity definitions in other ontologies" - I'm not arguing this - I think a 
distinction *is* needed.

(If you had used entity "description" instead of entity "definition" (implying 
possible arbitrary metadata about an entity), then I'd be less clear cut, but at 
some level I think this group does want to have some notion of provenance from 
other descriptions.  My mental model has provenance as a subset of arbitrary 
entity descriptions; I imagine a property like "hasProvenance", which may be a 
subproperty of something like rdfs:seeAlso.  As for exactly what constitutes 
provenance information, I think that is somewhat open.)

"the mapping of instances of the classes 'comet' and 'comet-near-star' to 
provenance entities is not part of the model" - I'm having trouble with two 
terms here: "mapping" and "entity".  I think we have adopted the term "entity" 
(pro tem, at least) to be roughly "something about which we wish to express 
provenance".  I don't know what you mean by "mapping instances" here, but I'm 
guessing something like "relating".  In any case, I can't find an interpretation 
of this that I'd agree with.

That is, I think the relationship between entities and provenance *is* part of 
the model, just not part that is covered by Simon's definition.  Again, we seem 
to be back to the problems of considering term definitons in isolation.

> How do we know that "Halley's Comet" and "Halley's comet near the sun" 
 > are related and not 'representations' of different 'stuff'?
> ("Kahoutek-near-the-sun" Is not an IVP of/not related to "Halley's comet".)

That's a question of epistemology.  In my mental model, we know that if it is 
asserted.  We might even define a property for it ... which is what I saw 
Simon's definition edging towards.

> What terms/description of 'representation' and 'stuff' is current? 
> Do we still agree that there is something out there behind/beyond entities?

I understand the current term here is "entity" for anything about which we might 
wish to express provenance.  Like a web _resource_, an _entity_ can be 
identified by a URI (but is not required to be).  In my mental model, _entities_ 
may be related to each other by a notion like IVP, though I prefer to think of 
that as "contextual constraint" which can be expressed in terms of 
truth-of-assertions.

> Where does IVP stand?

See above for a personal take.

> What I'm picking up for the most part is that IVP can't be hierarchical in general,
> which I think has faded as we tried to talk about properties of one entity having 
 > to be immutable in an IVP of it. Technically, I'm not sure we ever said that 
there
> couldn't be properties going in the reverse direction
> (allowing A IVP of B and B IVP of A), and my original arguments were that
> invariance was relative to the processes being discussed which also implies
> IVP relationships could go in both directions depending on the processes you
 > wanted to talk about. Is the current discussion just reaffirming that we're not
> talking about hierarchies of invariance, or is there more to the discussion
> about how the IVP relationship has to change?

I see IVP being hierarchical, but I do think that it is transitive:

Comet -> Halley's comet       -> Halley's comet near sun
       -> comet near sun
       -> Kahoutek             -> Kahoutek near sun

(where *all* of the things (sensu colloq.) mentioned above are _entities_)

So we have:

Halley's comet          _IVP_   comet
Kahoutek                _IVP_   comet
Comet near sun          _IVP_   comet

Halley's comet near sun _IVP_   Haley's comet
Halley's comet near sun _IVP_   comet near sun
Halley's comet near sun _IVP_   comet

Kahoutek near sun       _IVP_   Kahoutek
Kahoutek near sun       _IVP_   comet near sun
Kahoutek near sun       _IVP_   comet

But NOT other relations that would be needed if IVP were to be hierarchical.

I'm sorry of all this is a bit laboured, but I hope this helps to clarify my 
understanding.

#g
--

>> -----Original Message-----
>> From: public-prov-wg-request@w3.org [mailto:public-prov-wg-
>> request@w3.org] On Behalf Of Simon Miles
>> Sent: Wednesday, July 13, 2011 8:36 AM
>> To: Provenance Working Group WG
>> Subject: Re: Models and their use
>>
>> Jim, Graham,
>>
>> Reading through your comments, I'm pretty much in agreement with them.
>> The discrepancy between my view and Jim's is, I think, just a matter of what
>> we assume is being defined at the moment (i.e. by entity/thing).
>>
>> As in Graham's last mail, I am assuming that we are first defining any
>> (contextualised) entity ((1) in Graham's classification).
>>
>> I fully agree with you that assertion/observation/description (2) is also an
>> important and distinct concept. However, I see it as secondary to the idea of
>> entity in the model and, as Graham says, a description is itself a kind of
>> entity. This may be comparable to agents or process executions, i.e. agents,
>> executions and descriptions are all particularly important (for provenance)
>> subclasses of entity.
>>
>> And I think this difference in our views about what was being defined by
>> "thing" nicely illustrates the original point I was trying to make about the
>> conflation in the definition :-)
>>
>> Thanks,
>> Simon
>>
>> On 13 July 2011 11:01, Graham Klyne <GK@ninebynine.org> wrote:
>>> Jim,
>>>
>>> I've been thinking about your comments, and have come to a view that
>>> there are two things going on here, which are not being clearly
>> distinguished:
>>> 1. an entity constrained to some context
>>>
>>> 2. observations or descriptions of an entity
>>>
>>> which when combined can model observations/descriptions of an entity
>>> constrained to some context.  I have been focusing on (1), with the
>>> expectation that (2) would be dealt with separately in the model,
>>> where provenance is a kind of description.  If I understand correctly,
>>> you are particularly concerned to distinguish between entity and
>>> description.  It seems to me that "bob" has been adopted variously to fulfil
>> both these distinctions.
>>> ...
>>>
>>> Example: suppose we're interested in Halley's comet, and in particular
>>> in the periods when it is close to the sun or visible from earth.  So
>>> we have two
>>> concepts:  Halley's comet and Halleys comet when close to Earth.  To
>>> my mind, these are both *entities* (sensu F2F1).  Any description that
>>> is true of Halley's comet generally should also be true of it when
>>> close to Earth, but there are many other assertions are true the
>>> constrained Halley's comet that are probably not true at all times
>>> (e.g. the appearance of a tail due to expulsion of gas and dust caused by
>> solar heating).
>>> The page http://en.wikipedia.org/wiki/Halley's_Comet is a
>>> *description* of Halley's comet.  Being a Wikipedia page, it probably
>>> changes over time.  So we may wish to discuss it as it exists in a
>>> particular period of time.  Today, for example, it contains a list of
>>> 95 references indicating sources of information used in the page.
>>> Thus we may expect this page to be a description of Halley's comet for
>>> its entire lifetime, but needs to be constrained to make statements
>>> about the number of references it contains.  In this respect, the page is
>> both an "entity" and a "description" of an entity.
>>> The page at http://en.wikipedia.org/wiki/Halley's_Comet also has a
>>> brief description of a Cuneiform-inscribed clay tablet which is both
>>> an entity in its own right, with its own description and provenance,
>>> *and* a record of observation of Halley's comet.  I don't think we can
>>> easily disjoin the class of descriptions from the class of entities.
>>>
>>> Thus, I perceive that the notion of constraint so that some aspects of
>>> a constrained entity are invariant needs to be dealt with separately
>>> from the notion of description, which often (but not always, I think)
>>> applies to a constrained form of some entity.
>>>
>>> Does this make any sense?
>>>
>>> #g
>>> --
>>>
>>>
>>> Jim McCusker wrote:
>>>> My issue is more with Simon's desire to conflate things with the
>>>> descriptions of those things. We need to be able to say "x, as
>>>> described by y", which is a separate issue from relating "x1" as an
>>>> invariant view of "x2".
>>>>
>>>> "x as described by y" can be done in semweb using a URI for X and the
>>>> URI for a named graph or graph literal for y, assuming that there are
>>>> assertions in y about x. Another alternative is that y can be
>>>> discussed as an information artifact, as in the Information Artifact
>>>> Ontology (http://code.google.com/p/information-artifact-ontology).
>>>> Since x changes over time, we need something that nails down what was
>>>> actually "seen", or at least, claimed when the agent identified x in
>>>> its context.
>>>>
>>>> A BOB is the y in the above paragraph, and I think that the fact that
>>>> it's something that's describing an x, it must have the extra
>>>> qualification in place in its name.
>>>>
>>>> Jim
>>>>
>>>> On Tue, Jul 12, 2011 at 3:27 PM, Graham Klyne <GK@ninebynine.org>
>> wrote:
>>>>> [Off-list]
>>>>>
>>>>> Jim,
>>>>>
>>>>> I had some small reservations about Simon's definition, but I felt
>>>>> that it was such a big improvement over what we currently have that
>>>>> I didn't want to muddy the waters just yet by adding qualifications
>>>>> to my support :)
>>>>>
>>>>> (Specifically, I would remove "and something more is invariant about
>>>>> B" from the efinition of invariant view, so that anything can be an
>>>>> invariant view of itself (or not excluded from so being) - which I
>>>>> think is one of the concerns you raised.)
>>>>>
>>>>> Apart from that, I think there is an aspect of an invariant view
>>>>> that is in some sense fundamentally subsumptive -- there is a
>>>>> distinct sense that A and B are generally the same, except that one may
>> be more constrained.
>>>>> But, more importantly, I think we need to be looking to say less, not
>> more.
>>>>> I feel that Simon's definition captures close to what we need to say
>>>>> without adding too much more.
>>>>>
>>>>> In this, I'm arguing for the minimum useful semantics - it's easier
>>>>> to add (or layer) constraints later than to remove them from an
>>>>> established defintion.  By providing a little as we can for people
>>>>> to disagree with, I think we maximize the potential for take-up of the
>> WG outputs.
>>>>> #g
>>>>> --
>>>>>
>>>>>
>>>>> Jim McCusker wrote:
>>>>>> On Tue, Jul 12, 2011 at 12:02 PM, Graham Klyne <GK@ninebynine.org>
>> wrote:
>>>>>>> Simon Miles wrote:
>>>>>>>> To understand the consequences of the above points, I suggest
>>>>>>>> alternative definitions at the link below:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>> http://www.w3.org/2011/prov/wiki/Talk:F2F1ConceptDefinitions#Enti
>>>>>>>> ty_and_IVP_of
>>>>>>> +1
>>>>>>>
>>>>>>> I think this is a big improvement over what we have.
>>>>>> I like the Entity definition, but I'm not sure how we then go about
>>>>>> qualifying assertions about Entities. We need a way of making those
>>>>>> assertions (which is what BOBs were for) and a way of relating
>>>>>> Entities that are the same, even if they aren't mathematically the
>>>>>> same (different state, different aspect, etc.). IVP of as it's
>>>>>> defined there is not quite enough, since it only allows for
>>>>>> relations between entities that have subsumptive (a is IVP of b,
>>>>>> therefore a has all the states of b plus some).
>>>>>>
>>>>>> Jim
>>>>>> --
>>>>>> Jim McCusker
>>>>>> Programmer Analyst
>>>>>> Krauthammer Lab, Pathology Informatics Yale School of Medicine
>>>>>> james.mccusker@yale.edu | (203) 785-6330
>>>>>> http://krauthammerlab.med.yale.edu
>>>>>>
>>>>>> PhD Student
>>>>>> Tetherless World Constellation
>>>>>> Rensselaer Polytechnic Institute
>>>>>> mccusj@cs.rpi.edu
>>>>>> http://tw.rpi.edu
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>> __________________________________________________________
>> ____________
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>> __________________________________________________________
>> ____________
>>
>>
>> --
>> Dr Simon Miles
>> Lecturer, Department of Informatics
>> Kings College London, WC2R 2LS, UK
>> +44 (0)20 7848 1166
> 
> 
> 
Received on Thursday, 14 July 2011 06:42:06 GMT

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