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Re: PROV-ISSUE-467 (activity-start-req-trigger): Do activity start/end always require trigger? [prov-dm-constraints]

From: Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk>
Date: Thu, 9 Aug 2012 11:23:45 +0100
Message-ID: <CAPRnXtneTj+Kn7NWDz0yd0sEMU0Ro5E8FkmQDbtRmc5GE0pDVg@mail.gmail.com>
To: James Cheney <jcheney@inf.ed.ac.uk>
Cc: Luc Moreau <l.moreau@ecs.soton.ac.uk>, public-prov-wg@w3.org
On Thu, Aug 9, 2012 at 10:59 AM, James Cheney <jcheney@inf.ed.ac.uk> wrote:
> 1. [status quo] - allow expanding the trigger parameter to an existential variable denoting an unknown (but definite) trigger entity
> 2. change the trigger parameter to be non-expandable, so that "-" means "absent trigger", as with plan and other non-expandables.
>
> So we'll resolve this issue by taking whichever of the above has the stronger consensus?

Right, simple options.


For #2 - I assume that if the trigger is absent, then the starter
activity should also be -. (To avoid recreating non-triggering
wasStartedByActivity). If the starter activity is given, then we
simply don't know the identity of the trigger. Thus Inference
wasStartedBy-inference should always run, unless they are both -.

Example change to inference rule:



Inference 9 (wasStartedBy-inference)
IF wasStartedBy(_id; a,e1,a1,_t,_attrs) and either e1 or a1 are not
the placeholder -, THEN there exist _gen and _t1 such that
wasGeneratedBy(_gen; e1,a1,_t1,[]).

Remark:
If both the trigger e1 and the starter activity a1 is the placeholder
-, this indicates that there is no trigger (and thus no activity
generating that trigger), and this inference rule does not apply. If
the starter activity is given, then the trigger e1 is present, but
unknown.

(and equivalent for wasEndedBy-inference)

-- 
Stian Soiland-Reyes, myGrid team
School of Computer Science
The University of Manchester
Received on Thursday, 9 August 2012 10:24:33 UTC

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