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Re: Definitions and provenance and invariance

From: Paolo Missier <Paolo.Missier@ncl.ac.uk>
Date: Sun, 26 Jun 2011 19:06:09 +0100
Message-ID: <4E077511.2070704@ncl.ac.uk>
To: public-prov-wg@w3.org
once again, I think I need a clarification of the difference between a /property/ being invariant (valid within a scope) and its 
/value/ being constant (within a scope, interval, etc).

In the File example  http://www.w3.org/2011/prov/wiki/ConceptInvariantViewOnThing#Comment_by_Stian__24_June_2011
Stian wrote:  "The Printout content is an*invariant*property, but a variant property of the Document."

This seems to refer to the value of property "content" (which will not change for the Printout), rather than to the property itself?

-Paolo

On 6/26/11 3:00 PM, Paul Groth wrote:
> Hi Simon,
>
> Thanks for the clarification. That was what I thought but just wanted to
> check.
>
> cheers,
> Paul
>
> Simon Miles wrote:
>> Paul - As I understood the intent, the provenance of a thing would be
>> assertions about the invariant properties of that thing, yes. You
>> couldn't say much about the variant properties other than that they're
>> variant. However, it may be unnecessary to explicitly "declare"
>> properties to be invariant.
>>
>> Paolo - I agree that we shouldn't mix up fixed assertions on the
>> values of properties with those properties being invariant. Though I
>> don't think anyone has suggested the former - even if properties were
>> declared to be invariant (as I think Paul's question implied), that
>> would not be the same as declaring what their values were, let alone
>> not allowing those declarations to change.
>>
>> Thanks,
>> Simon
>>
>> On 26 June 2011 12:12, Paolo Missier<Paolo.Missier@ncl.ac.uk>   wrote:
>>> I would say you can talk about the provenance of that view. But, to be clear, the fact that some properties are "declared" to be
>>> fixed (constant), for example by saying that "the creator is {invariant, immutable, constant,...}",  should have nothing to do with
>>> provenance.  It's in the semantics of the "thing" and its properties, I hope we agree on this? In a data model, one would enforce a
>>> constraint to avoid "creator" being updated, to reflect the intended semantics of the property. Is this what we mean by "fixed"?
>>> And even then, that's assuming too much already: updates to "creator" may be acceptable if the original value is found to be wrong,
>>> for example.
>>>
>>> -Paolo
>>>
>>> On 6/26/11 9:56 AM, Pgroth wrote:
>>>> For my clarification, once an asseter  has an invariant view of some stuff the asserter can talk about the stuff's provenance with respect to the set of properties that have been declared fixed?
>>>>
>>>> Thanks
>>>> Paul
>>>
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Received on Sunday, 26 June 2011 19:34:32 GMT

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