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Re: Comments of PROV-DM document (Section 2.1 and 3)

From: Paolo Missier <Paolo.Missier@ncl.ac.uk>
Date: Wed, 12 Oct 2011 09:32:27 +0100
Message-ID: <4E95509B.40304@ncl.ac.uk>
To: Satya Sahoo <satya.sahoo@case.edu>
CC: Luc Moreau <L.Moreau@ecs.soton.ac.uk>, Provenance Working Group WG <public-prov-wg@w3.org>
Hi Satya,

let me fast forward to the events bit as I was involved in the "traffic ticket" discussion on the latest call.   But I may be simply 
reiterating what Luc stated in a earlier mail.

On 10/11/11 11:39 PM, Satya Sahoo wrote:
>
>     >
>     > 3. This specification assumes that a partial order exists between
>     > events.
>     >
>     > Issue: Are we excluding overlapping events or events that are
>     > "contained" in other events?
>
>     Events are instantaneous. Hence, there is no overlap and
>     containment. Two events occurs at the same instant or not.
>
> We briefly discussed the issue of ordering of events during the PROV-O/M call yesterday and the example we discussed may be 
> relevant - an event "issuance of a traffic ticket to X" can be viewed as instantaneous (total of traffic tickets issued per year 
> in City A) or stated to have a duration (10mins). Further, the event may contain events as "ran the stop sign", "handed over 
> license", "signed the ticket" etc.
>
> We should be able to model all the above set of events in PROV.
Events have no time span because they mark particular instants in time that it is useful to be aware of (those listed below).  So 
events are distinct from activities by definition. And there is nothing domain-specific about events. They are core.

The four event types that are needed /for this purpose/ are listed in sec 5.5.6.1:

 1. Generation of a characterized thing by an activity: identifies the final instant of a characterized thing's creation timespan,
    after which it becomes available for use.
 2. Use of a characterized thing by an activity: identifies the first instant of a characterized thing's consumption timespan.
 3. Start of an activity: identifies the instant an activity, represented by a process execution, starts;
 4. End of an activity: identifies the instant an activity, represented by a process execution, ends.

"issuance of a traffic ticket" should be modelled   as a pe, with whatever time duration there is. It begins (3), generates a ticket 
(1), and ends (4). It may presumably use the driver's data as input, which is available at a certain point (2). The constraints 
govern the partial ordering amongst these four events which makes the assertions on pe, use, and generation consistent with each 
other. When one or more of these events are not specified, then your ability to enforce consistency is diminished.
I am not sure there is any more than this?

>
>     >
>     > 4. In our conceptualization of the world, punctual events, or events
>     > for short, happen in the world, which mark changes in the world, in
>     > its activities, and in its things.
>     >
>     > Issue: This definition of event seems to be a specialization of a PE?
>     > What are the distinguishing features (if any) of an event vis-a-vis
>     > PE?
>
>     I don't see why they seem to be a specialization. Is it because event duration=0?
>     We have four types of events, two of which are start and end of PE.
>     So, to me they are very distinct from PE.
>
> Maybe. For example "issuance of a traffic ticket" may be viewed as an instantaneous event or a event with duration depending on 
> the requirement of the provenance application.
see above

-Paolo
Received on Wednesday, 12 October 2011 08:33:06 GMT

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