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

From: Luc Moreau <l.moreau@ecs.soton.ac.uk>
Date: Wed, 12 Oct 2011 20:52:35 +0100
Message-ID: <EMEW3|23b04c02ea52660abe10fab46310cfe3n9BKqe08l.moreau|ecs.soton.ac.uk|4E95F003.2050707@ecs.soton.ac.uk>
To: Satya Sahoo <satya.sahoo@case.edu>
CC: Provenance Working Group WG <public-prov-wg@w3.org>, Paolo Missier <Paolo.Missier@ncl.ac.uk>
HI Satya,

In the proposed model,
- there is a point when a PE is deemed to have started, and before that 
it is not
- there is a point when a PE is deemed to have ended, and before that it 
is not
- there is a point when an entity is deemed to have existed, and before 
that it did not existed
- there is a point when an entity is deemed to have been used, and 
before that it had not

These points are named events. We can change the name ,if we want, to 
transition, interval
boundary, or whatever.

If you believe that your PE is not usefully modelled by an instantaneous 
start, e.g. because you
want to describe all operations involved in, say, the start of a nuclear 
plant, you should model
this starting activity as a PE. This PE, in turn, will have start and 
end in a similar way.

So, I am arguing, that the construct to model any activity in the world 
is a PE. We mark each
PE by a beginning and end. We call them events (and likewise for entities).

Luc



On 12/10/2011 20:16, Satya Sahoo wrote:
> Hi Luc,
> >The notion of event introduced in the document is different. It 
> should be understood as "a transition that
> >changes the state of the system".
>
> The current definition of event from PROV-DM document: "In our 
> conceptualization of the world, instantaneous events, or *events* for 
> short, happen in the world, which mark changes in the world, in its 
> activities, and in its things."
>
> Given that instantaneous is *always* defined with respect to a unit of 
> time:
> Instantaneous: "done, occurring, or acting without any perceptible 
> duration of time" - Webster dictionary
>
> and there is still no absolute unit of time corresponding to "instant" 
> [1], each application (provenance and others) use a relative notion of 
> "instantaneous".
>
> Hence, what is an "instantaneous event" for provenance application A 
> maybe a "long-running event" (aka PE in your language) for another 
> provenance application according to what each application considers to 
> be "instantaneous" - 1 second, 1 millisecond, 1 nanosecond etc.
>
> A scientist can assert that a workflow instance "mappingGenetoProtein" 
> "started" at 11:00am US ET and "ended" at 11:15amET - so 
> "mappingGenetoProtein_start" and "mappingGenetoProtein_end" are events 
> according to your current definition.
>
> But, a programmer views the "mappingGenetoProtein_start" as a PE since 
> it has the following events (according to your definition) - "load 
> gene sequence" at 11:00:05am ET, "create packet with gene sequence and 
> header information" at 11:00:20am ET, and "send request to NCBI BLAST 
> website at 11:00:50am ET etc.
>
> It is important to note that "nothing" happened between 11:00:00am ET 
> and 11:00:04am ET, but for the researcher the event of 
> "mappingGenetoProtein_start" occurs at 11:00am ET since the 
> granularity of time measurement for the researcher is hours and 
> minutes, not seconds.
>
> All the above listed events satisfy your current definition of event: 
> "instantaneous" "mark changes in the world, in its activities, and in 
> its things."
>
> Hence, to paraphrase "one person's data is another person's metadata", 
> the *current definition* of event allows it to be interpreted as "one 
> person's event is another person's PE".
>
> Overall, there does not seem to be any need for this WG to mandate 
> that an event has to be instantaneous (and not be able to define what 
> is instantaneous). We are using events to enable ordering - allowing 
> events to span time duration does not negate this capability. Each 
> application can decide on the granularity of time to be associated 
> with an event and still use events for relative ordering.
>
> What do you think?
>
> > You come to this discussion with a different meaning of event, and 
> try to shoe horn it into the notion
> >of event in the model.
> Unfortunately Luc, just the "event" page on Wikipedia lists 19 
> meanings of the term "event" [2] - there are many more definitions of 
> "events" in computer science - from system events to user events 
> (basis of event-driven programming). The issue is not of shoehorning 
> or unshoding - but a better understanding of the issues.
>
> > We do not have a containment relationship for PEs.  Whether we want 
> one is open to debate.
> I think it is necessary - a workflow instance PE may contain many 
> "atomics" PEs.
>
> Thanks.
>
> Best,
> Satya
>
>
> [1] http://en.wikipedia.org/wiki/Instant
> [2] http://en.wikipedia.org/wiki/Event
>
> On Wed, Oct 12, 2011 at 3:48 AM, Luc Moreau <L.Moreau@ecs.soton.ac.uk 
> <mailto:L.Moreau@ecs.soton.ac.uk>> wrote:
>
>
>     Hi Satya,
>
>     What you are describing here is various activities (which we
>     represent as process execution expressions).
>     The notion of event introduced in the document is different. It
>     should be understood as "a transition that
>     changes the state of the system".  Start of a PE and end of a PE
>     are examples of such transitions/events.
>
>     You come to this discussion with a different meaning of event, and
>     try to shoe horn it into the notion
>     of event in the model. It does not work.  The examples of what you
>     describe as events should be mapped
>     to PEs.
>
>     We do not have a containment relationship for PEs.  Whether we
>     want one is open to debate.
>
>     Luc
>
>
>     On 10/11/2011 11:39 PM, Satya Sahoo wrote:
>
>         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.
>
>
>     -- 
>     Professor Luc Moreau
>     Electronics and Computer Science   tel: +44 23 8059 4487
>     <tel:%2B44%2023%208059%204487>
>     University of Southampton          fax: +44 23 8059 2865
>     <tel:%2B44%2023%208059%202865>
>     Southampton SO17 1BJ               email: l.moreau@ecs.soton.ac.uk
>     <mailto:l.moreau@ecs.soton.ac.uk>
>     United Kingdom http://www.ecs.soton.ac.uk/~lavm
>     <http://www.ecs.soton.ac.uk/%7Elavm>
>
>
Received on Wednesday, 12 October 2011 19:53:20 GMT

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