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Re: PROV-O comments

From: Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk>
Date: Tue, 29 Nov 2011 23:36:36 +0000
Message-ID: <CAPRnXt=g3+FwbOHRfvarAi-tdrtJd+UbViF5Nz8UcFuReiN8iA@mail.gmail.com>
To: Simon Miles <simon.miles@kcl.ac.uk>
Cc: Provenance Working Group WG <public-prov-wg@w3.org>
I think philosophically and physically you can never truly have a
non-divisive "instant" unless it is defined at Planck time. (~ 10^-44 s)

Practically we know that we all make simplifications. I can say I bought a
Corolla from Luc at 2011-04-12 13:45 as an instant. I am not detailing how
many seconds it took to sign the papers and hand over the key, but another
asserter (using different activities) might do so, and would classify his
Purchase activity to last from 13:44:42 to 13:45:36, ie. a
time:ProperInterval.

A third asserter might even disagree with the (instant) boundaries of that
interval, because although I did finish pronouncing "OK" at 13:44:42.000,
Luc could not hear so until 13:44:42.006 due to the speed of sound.

So as different accounts (and this might be a big argument for doing
subprocesses as nested accounts) can have different granularity, "instant
events" grow to activities with duration. But we can't cater for the
quantum physicist at all granularities.

Note: The WG which proposed time.owl *draft* has long gone, I don't know if
the document can be adopted by another WG for such clarifications.
On Nov 29, 2011 6:22 PM, "Simon Miles" <simon.miles@kcl.ac.uk> wrote:

> Hi Stian,
>
> Thanks for the clarification. That's fine, but the text does still say
> that instants can have "no interior points". From what you say, that
> is simply something that can't be enforced, and we distinctly would
> not want it to be, so it seems misleading to explain it that way.
> Maybe what is meant is "no interior points for this asserter at this
> moment", but that doesn't seem too helpful.
>
> Thanks,
> Simon
>
> On 29 November 2011 16:39, Stian Soiland-Reyes
> <soiland-reyes@cs.manchester.ac.uk> wrote:
> >
> > On Nov 24, 2011 3:13 PM, "Simon Miles" <simon.miles@kcl.ac.uk> wrote:
> >
> >> Maybe a philosophical point, but is an Instant, as referred to in Sec
> >> 3.1.4 and subclassed to Time in 3.1.10.1, really helpful in provenance
> >> data? It is defined as having "no interior points", but can one
> >> asserter ever know that what they refer to as an instant will not need
> >> to be decomposed by a future asserter?
> >
> > As we are using time.owl here you are free to assert times using what
> > granularity and time.owl properties fit, for instance only minutes.
> >
> > time.owl does not provide any precision notion (you could add a cusbtom
> > one), but neither does it say much about time equivalense for instances.
> > (interval have lots of time relations)
> >
> > So I believe there would be no conflicts, although in general it would
> make
> > more sense to talk about intervals between different activities, etc.
>
>
>
> --
> Dr Simon Miles
> Lecturer, Department of Informatics
> Kings College London, WC2R 2LS, UK
> +44 (0)20 7848 1166
>
> Provenance in Agent-mediated Healthcare Systems:
> http://eprints.dcs.kcl.ac.uk/1273/
>
>
Received on Tuesday, 29 November 2011 23:37:05 UTC

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