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Re: PROV-ISSUE-104 (time-class): How to relate start/end time to PE, use, generation, etc [Formal Model]

From: Paul Groth <p.t.groth@vu.nl>
Date: Wed, 28 Sep 2011 18:17:17 +0100
Message-ID: <091B5BC0-C6F2-45D0-BB12-72A24DAD77B7@vu.nl>
To: Provenance Working Group WG <public-prov-wg@w3.org>
Formalizing Time is outside the scope of the working group. We need to recognize that not everything will be able to be expressed otherwise we won't have interoperability.

Cheers
Paul


On Sep 28, 2011, at 16:02, Provenance Working Group Issue Tracker <sysbot+tracker@w3.org> wrote:

> 
> PROV-ISSUE-104 (time-class): How to relate start/end time to PE, use, generation, etc [Formal Model]
> 
> http://www.w3.org/2011/prov/track/issues/104
> 
> Raised by: Stian Soiland-Reyes
> On product: Formal Model
> 
> The conceptual model allows the optional time for:
> 
> processExecution ( identifier [ , recipeLink ] , [ time ] , [ time ] , other-attribute-values )
> wasGeneratedBy ( identifier , identifier , generationQualifier [, time] )
> used ( identifier , identifier , useQualifier [, time] ) 
> 
> 
> It is defined as:
> 5.5.6 Time
> Time instants are defined according to xsd:dateTime [XMLSCHEMA-2].
> It is optional to assert time in use, generation, and process execution expressions.
> 
> I don't particularly like making time a data property like this (not allowing you to say anything about how the time was measured, uncertainty, (see neutrino experiment), relative frame of reference, etc; and does not allow non-gregorian time (seconds only, or timeframes, cpu steps, etc) - that's probably a separate issue.
> 
> In the formal model we have a class prov:Time - but no way to connect this to ProcessExecutions. Associating them to use/generation, etc is strongly related to ISSUE-103 - but for PEs it should at least be easy to do:
> 
> prov:ProcessExecution prov:startedAt [ 
>    a prov:Time; 
>    prov:time "2011-02-19T12:03:12Z"^xsd:datetime ] ;
>  prov:endedAt [ # .. 
>    a prov:Time; 
>    prov:time "2011-02-19T12:05:10Z"^xsd:datetime ] ;
>  ]  .
> 
> the use of a prov:Time class will open for application extensions for the concerns I am thinking of. 
> 
> If we introduce prov:follows and prov:preceeds as suggested by the conceptual model in http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#event-ordering, it would be possible for asserters who only know about event ordering to use prov:Time instances which only are described using followed/preceeded with other Time instances.
> 
> (I guess these terms are in present tense in the conceptual model because we are talking about Time - the two times would always be followed/precededed by each-other - but we could change it to past tense for consistency)
> 
> 
> 
> 
Received on Wednesday, 28 September 2011 17:17:48 GMT

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