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Re: Models and their use

From: Paul Groth <p.t.groth@vu.nl>
Date: Thu, 14 Jul 2011 09:13:02 +0200
Message-ID: <19BD3536-8D59-4896-878F-BEF65FF7DDEF@vu.nl>
CC: "Myers, Jim" <MYERSJ4@rpi.edu>, Simon Miles <simon.miles@kcl.ac.uk>, Provenance Working Group WG <public-prov-wg@w3.org>
To: Graham Klyne <GK@ninebynine.org>
Hi All

There's a lot to comment on this thread but just for clarification, here's the mapping from the old terms to the terms from the F2F.

Old = New
Stuff = Entity
Thing = Bob or Entity State

I hope this helps the conversation.

Finally I would suggest that the participates divide issues into two threads if possible (e.g. Model vs ivp). Otherwise it's difficult for people to track and the messages get long and hard to tease apart.


On Jul 14, 2011, at 8:40 AM, Graham Klyne <GK@ninebynine.org> wrote:

> 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
>>> __________________________________________________________
>>> ____________
>>>> This email has been scanned by the MessageLabs Email Security System.
>>>> For more information please visit http://www.messagelabs.com/email
>>> __________________________________________________________
>>> ____________
>>> --
>>> Dr Simon Miles
>>> Lecturer, Department of Informatics
>>> Kings College London, WC2R 2LS, UK
>>> +44 (0)20 7848 1166
Received on Thursday, 14 July 2011 07:05:35 UTC

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