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Re: PROV-ISSUE-184: Section 2.1.2 (PROV-DM version as on Nov 28th) [prov-dm]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Fri, 09 Dec 2011 10:01:52 +0000
Message-ID: <EMEW3|cd00d00186de10fe8190974dbcb8d809nB8A1y08L.Moreau|ecs.soton.ac.uk|4EE1DC90.5090101@ecs.soton.ac.uk>
To: Jim McCusker <mccusj@rpi.edu>
CC: public-prov-wg@w3.org
Hi Jim,

I have been thinking about how to address your specific point 1, also 
raised by Satya.

In a generation, what we care about is the point at which the entity 
becomes available for consumption by others.
Before that, it's not an entity yet (or it is not this entity being 
generated).  So, to some extent, calling the whole
of generation an event (forget the choice of word for now) is not what 
was intended.  The event is the point at which
generation is complete.

This is actually nice reflected in Olaf and Jun's provenance vocabulary 
[1], where they have a similar concept,
called Data Creation defined as:

    /DataCreation is a class that represents the completed creation of a
    data item./


Note the choice of word *completed*.

I therefore propose to change the definition of Generation [2] as follows.

/In PROV-DM, a generation record is a representation of a world event, 
the completed creation of a new entity by an activity. This entity did 
not exist before this event; this entity is available for usage after 
this event.
/
With this, we are not saying that creation of an entity is the event, 
it's the completed creation that is.  It's also also fine, I believe, to 
regard this
as instantaneous.  Also, if somebody wants to model the actual creation, 
it is also fine, they can use activities for that.

For usage, we would take a similar approach. In the provenance 
vocabulary, they use the completed access to a data
structure, but this is not right for what we want. Instead:

/In PROV-DM, a usage record is a representation of a world event: the 
start of an entity consumption by an activity. Before this event, this 
entity was not consumed or used in any form or shape by the activity, 
totally or partially. /

These definitions are now exactly in line with those in [3].

Regarding your point [2], I also came to the conclusion that for this 
community, we should not use the word event.
Regarding your point [3], I am against renaming activity into event. 
Because then, we would confuse another bunch of people.

So, I would suggest we ban the word 'event' from the prov-dm document.

Another term commonly used in process algebra for this concept is 
/action/.  The 4 actions (entity generation/entity usage/activity 
start/activity end) have effects on the system.

Thoughts,
Luc


[1] http://trdf.sourceforge.net/provenance/ns.html#sec-DataCreationClasses
[2] 
http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#dfn-Generation
[3] 
http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#types-of-events

On 12/08/2011 11:52 PM, Jim McCusker wrote:
> I have some of the same concerns as Satya around the idea of 
> wasGeneratedBy, used, et al. being described as instantaneous events.
>
> 1) The use of an entity and generation of an entity are not 
> instantaneous things (although they can be recorded as such), but are 
> things that occur through time.
>
> 2) Calling these things events results in the sort of confusion that 
> we are seeing from Satya. The Activity is the event, and should 
> therefore be called Event.
>
> 3) Relying on terminology from process algebra is fine for people who 
> are familiar with it, but we want to provide that sort of theoretical 
> foundation to those who are not familiar with those term uses, and 
> would find the distinction between "event" and "activity" less then 
> helpful.
>
> Jim
> -- 
> Jim McCusker
> Programmer Analyst
> Krauthammer Lab, Pathology Informatics
> Yale School of Medicine
> james.mccusker@yale.edu <mailto:james.mccusker@yale.edu> | (203) 785-6330
> http://krauthammerlab.med.yale.edu
>
> PhD Student
> Tetherless World Constellation
> Rensselaer Polytechnic Institute
> mccusj@cs.rpi.edu <mailto:mccusj@cs.rpi.edu>
> http://tw.rpi.edu

-- 
Professor Luc Moreau
Electronics and Computer Science   tel:   +44 23 8059 4487
University of Southampton          fax:   +44 23 8059 2865
Southampton SO17 1BJ               email: l.moreau@ecs.soton.ac.uk
United Kingdom                     http://www.ecs.soton.ac.uk/~lavm
Received on Friday, 9 December 2011 10:02:52 UTC

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