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Re: PROV-ISSUE-470 (wasDerFrom-strictly): wasDerivedFrom requires use strictly before generation - why? [prov-dm-constraints]

From: Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk>
Date: Wed, 8 Aug 2012 09:36:16 +0100
Message-ID: <CAPRnXtm-EiTbfc86=SJVw+X1LwMaHtOZ=nmBj5Ypd5_UHdAFsg@mail.gmail.com>
To: James Cheney <jcheney@inf.ed.ac.uk>
Cc: Provenance Working Group <public-prov-wg@w3.org>
On Mon, Aug 6, 2012 at 4:54 PM, James Cheney <jcheney@inf.ed.ac.uk> wrote:
> In internal discussion, we basically decided to make all of the constraints non-strict except the two involving derivation.  (The entity-generation-use one slipped through accidentally.)
> I see no reason to insist on the generation-use in derivation to be strictly-precedes, so I propose to weaken it to "precedes" unless anyone wants to make a case for it.

Sounds good. I just have one note (which should not affect this issue
unless you object) then about checking for time order constraints, as
the specification asks us to check for any loops with strictly
precedes. So if there are no derivations, you can't detect time order
violations, although all such such loops would then collapse to be
single instants. (Which timestamps might then informally suggest is
not the case).

Would there be any other way to detect the time order violations if
there are no derivations?

I suspect not, as there is no way in PROV alone to specifically state
time relations or durations - but there might be application specific
knowledge, for instance that ex:photocopying takes usually a second,
and ex:faxing takes usually at least 30 seconds, and thus a received
fax could not be photocopied at the same time as the fax was sent.

Stian Soiland-Reyes, myGrid team
School of Computer Science
The University of Manchester
Received on Wednesday, 8 August 2012 08:37:04 UTC

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