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Re: Some thoughts about the revised provenance Model document

From: Graham Klyne <graham.klyne@zoo.ox.ac.uk>
Date: Mon, 17 Oct 2011 18:48:05 +0100
Message-ID: <4E9C6A55.6030402@zoo.ox.ac.uk>
To: "Myers, Jim" <MYERSJ4@rpi.edu>
CC: Paul Groth <p.t.groth@vu.nl>, 'W3C provenance WG' <public-prov-wg@w3.org>
On 04/10/2011 15:24, Myers, Jim wrote:
>> To the extent that provenance assertions actually
>> *are* static attributes of that entity, ...
> - how do you make such assertions if static attributes aren't in the model?


Short answer: use a new predicate.

For example, if w is weather in London, then w1 = ( w such that On20111017(w) ) 
might be the weather in London on 2011-10-17.  Of course, the predicate can 
alternatively be construed as an attribute+value, which is close to what I 
alluded to when I said "To the extent that provenance assertions actually *are* 
static attributes of that entity".  (I think Quine discussed this kind of 
duality between predicates and properties of things in one of his assays.)


But I detect two different possible questions here:

- how do you make such assertions using the model if static attributes aren't in 
the model?


- how do you make such assertions by any means if static attributes aren't in 
the model?

And I realize my previous answer only addresses the latter case.

> If I understand your concerns correctly, they are partly due to language about entities being 'defined by' fixed attributes. I don't think it would be problematic, and in fact would probably agree with an alternate description that talks about entities being characterizations of things that limit their behavior over time (statements about object identities and states/characteristics have to remain true...)  and that characterizing attributes are a/the way in the provenance model to allow interchange of information about those limits (i.e. such attributes are not theoretically a defining aspect of entities but, in order to allow interchange and practical use of provenance information without knowledge of external object definitions/functionality, fixed attributes are defined.)
> Does this get us to a conceptual consensus?

That's certainly closer to what I had in mind.  In reading your earlier 
response, I realized I had not one but two niggles with the current formulation:

(1) the need to distinguish between characterizing and non-characterizing attributes

(2) The use of attributes at all.

I read your above formulation as allowing us to talk about characterizing 
attributes while completely ignoring other attributes, which AFAICT are 
irrelevant to description of provenance, addressing my concern (1)


My concern (2) is more subtle (and I could more easily let it be).

The goal that I perceive is to be able to say that some entity, say e1, is a 
characterization of a dynamic entity, say e, that allows us to make some 
provenance assertions whose truth is not ephemeral.  What I don't see is why one 
needs to know exactly how the constraints on e that correspond to e1 are 
determined.  If one makes a (true) provenance assertion about e1, then it seems 
to me that the necessary constraints exist for the provenance assertion about e1 
to be true.  My assumption is that the specific nature of the constraints is 
application or context dependent, and does not need to be part of the core 
provenance model.

For comparison: If we assert that a particular document d3 was derived from some 
datasets d1 and d2, we accept that as an assertion, without having to care about 
how that knowledge was obtained.  I'm applying a similar standard to the nature 
of constraints used to determine views (IVPs) for which provenance can be asserted.

Having said that, I note you mentioned in another message that the notion of 
attributes was needed to satisfy the provenance challenge.  I'm not aware of the 
details:  maybe there's a specific use-case here that could change my 
perspective on this...


>> then the existence of static attributes
>> (in the style of "characterizing attributes") may be inferred.  In this respect,
>> the static attributes are a consequence rather than a defining aspect of the
>> existence of meaningful provenance information.
>> #g
>> --
>>> Graham Klyne wrote:
>>>> Jim,
>>>> If I understand you correctly, the significance of attributes is for discovery
>>>> of of related resources.
>>>> My understanding is that the primary purpose of provenance is to
>> establish a
>>>> basis for trust, a reason to believe (or not) some information that is
>> presented
>>>> about some subject. It's not clear to me what need there is to use
>> attributes
>>>> for resource discovery to achieve this end. (But I may well be missing
>>>> something here.)
>>>> So, on this basis, there may be perfectly good reasons to have defined
>>>> attributes and values for discovery purposes, I'm not seeing why they are
>> needed
>>>> to achieve the goals of *provenance* information.
>>>> (But it's getting late here, and maybe I'm missing some key point in your
>>>> message.)
>>>> In summary: I think your concerns are reasonable, but what makes them
>> in scope
>>>> specifically for *provenance* information?
>>>> #g
>>>> --
>>>> On 29/09/2011 18:44, Myers, Jim wrote:
>>>>> Graham,
>>>>> How would we use provenance to find, for example, how Luc got to
>> Boston? It's
>>>>> clear if we have fixed attributes for name and location such that we
>> could
>>>>> query for an entity with name Luc that has an ivpOf relationship with an
>>>>> entity in Boston and then look at the provenance from there. How would
>> it
>>>>> work without fixed attributes in the prov model? I'm guessing that
>> you're
>>>>> thinking that we can find those attributes outside the language
>> somewhere
>>>>> (e.g. non-prov RDF statements) but what are the minimal requirements
>> there
>>>>> and what language/models exist that meet them? Can we only model
>> provenance
>>>>> of things for which ontologies have been developed? Presumably it has
>> to be
>>>>> possible to associate descriptive metadata with the entities through
>> some
>>>>> path (what relationship(s)?)? And it has to be clear which metadata is
>> fixed?
>>>>> You mention being able to infer across ivpOf relationships - is there one
>> set
>>>>> of inference rules for all possible descriptive metadata? Or do we need
>> to be
>>>>> able
>>>> to distinguish further between types of metadata?
>>>>> -->  As you can probably guess from the questions above, I'm concerned
>> that
>>>>> kicking fixed attributes out will end up being more complex and place a
>>>>> higher burden on users than keeping them in, but I may be
>> misunderstanding
>>>>> how such an alternative would work. Part of that concern is that I think I
>>>>> hear that modeling experts in this group can handle defining classes for
>>>>> different types of entities that would allow discovery by attribute, but
>> I'm
>>>>> concerned that being able to do this becomes a requirement for using
>>>>> provenance (versus asserting entities defined solely by attributes(entity,
>>>>> name=Luc) or perhaps in a mixed mode (e.g. an entity representing Luc
>> that
>>>>> 'hasBaseType' foaf:person and one representing him in Boston that also
>>>>> hasBaseType foaf:person and location=Boston as a fixed attribute.)
>> Again -
>>>>> perhaps I'm misunderstanding how discovery based on descriptive
>> information
>>>>> could be done if we don't have fixed characterizing attributes in the prov
>>>>> standard....
>>>>> Jim
>>>>>> 3. Do we need to model "Characterizing attributes"?
>>>>>> The notions of "characterizing attributes" have developed to derive the
>>>>>> relationship between different entities that are views of some
>> common
>>>>>> thing in the world. I am not convinced that we need to model these
>>>>>> attributes, and I'm not sure the way they are modelled can necessarily
>> apply
>>>>>> in all situations that applications might wish to represent.
>>>>>> At heart: when it comes to exchanging provenance information, why do
>> we
>>>>>> *need* to know exactly what makes one entity a constrained view of
>>>>>> another? What breaks (at the level of exchanging provenance
>> information) if
>>>>>> we have no access to such information? How are applications that
>> exchange
>>>>>> provenance information about entities for which they don't actually
>> know
>>>>>> about these attributes to know about their correspondences with real-
>> world
>>>>>> things?
>>>>>> I think the role of attributes here is mainly to *explain* some aspects
>> of the
>>>>>> provenance model, but they do not need to be part of the model.
>>>>>> To my mind, a simpler approach would be to allow for assertion of an
>> IVPof
>>>>>> type of relationship between entities, from which some useful
>> inferences
>>>>>> about any attributes present might flow, but I don't see the need for
>> the
>>>>>> attributes to be in any sense defining of the entities.
>>>>>> <aside>
>>>>>> My suggested definition of IVPof might be something like this:
>>>>>> A IVPof B iff forall p : (Entity ->  Bool) . p(B) =>  p(A)
>>>>>> where A, B are Entities, and the values of p are predicates on Entities.
>>>>>> </aside>
>>>>>> ...
>>>>>> #g
Received on Monday, 17 October 2011 17:49:50 UTC

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