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RE: Sample schema extension models

From: Jason Kinner <jason_kinner@dynamicdigitalmedia.com>
Date: Fri, 6 Jun 2003 08:20:03 -0400
To: "'Butler, Mark'" <Mark_Butler@hplb.hpl.hp.com>, <www-rdf-dspace@w3.org>
Message-ID: <00b001c32c25$f8b66160$0400a8c0@STARGATE>

Okay, about the "kinetic" thing, I was trying to point out that Events
and Actions represent how the system "moves" and that Situations
represent the resting state between these "moves", like someone
performing Tai Chi (to reach for an analogy).

I do find the separation of Event and Action a bit overstated, but it
does provide a way to model "acts of God" (an Event that has no
associated Action, e.g. - an earthquake).  An Event can also span time
and does not connote an "instant" nor even an atomic Event (hence,
subEventOf).  An Event can also collect multiple Actions via hasAction
(think of the Event as the New Year's Eve party in Times Square).  In
this way, both Situations and Events are "context" -- a Situation is the
context of the model between changes, and an Event is the context of the
changes.

-Jason

-----Original Message-----
From: www-rdf-dspace-request@w3.org
[mailto:www-rdf-dspace-request@w3.org] On Behalf Of Butler, Mark
Sent: Friday, June 06, 2003 6:49 AM
To: 'Jason Kinner'; www-rdf-dspace@w3.org
Subject: RE: Sample schema extension models


Hi Jason

Okay, I've been thinking this through, and I understand it a bit better
now.
One approach that helped is the one John Sowa uses in Knowledge
Representation i.e. converting the graphs into English sentences. I
actually
find this pretty helpful, so if we apply this to the first proposal we
get
(the numbers are for reference later)

1. There exists a Created called urn1 that precedes Situation urn3,
hasAction urn2 and hasPatient hdl:1234/123.

2. There exists a Create Action called urn2 that creates hdl:1234/123

3. There exists a Situation called urn3.

4. There exists a Modified Action called urn4 that follows Situation
urn3,
precedes Situation urn5 and hasPatient hdl:1234/123

5. There exists a Situation called urn5.

6. There exists an Item called hdl:1234/123;1, inContext urn3, with
title
"My Example" which is a phaseOf hdl:1234/123

7. There exists an Item called hdl:1234/123;2, inContext urn5, with
title
"Our Example" which is a phaseOf hdl:1234/123

where

hasPatient is a subProperty of involves

So before I couldn't see the point of urn3 and urn5 as they contain no
information apart from their type, but I had overlooked the inContext
property of hdl:1234/123;1 and hdl:1234/123;2. So that makes sense now.
However I'm still confused about why we need sentences 1 and 2 - can't
we
combine them into a single sentence e.g.

1.5 There exists a Create Action called urn1 that precedes situation
urn3,
that creates hdl:1234/123

i.e. that is more similar to sentence 4? Why are sentences 1 and 2
different
to 4?

Also I'm afraid I've got to pick on some of your terminology ... 

> I'll grant you that there is complexity, but I feel it is a 
> valid model.
> The need for Situations is that they represent the resting state of a
> portion of the model (the existential facet) /between/ events.  

Lagoze et al use the term existential facet, but I don't like it -
"facet"
has a very specific meaning in the library community - for example see
http://www.getty.edu/research/tools/vocabulary/aat/about.html

Lagoze's definition is "From the perspective of first-order logic, the
existential facet corresponds to there exists a situation in which an
instance of the entity exists with a property set and the universal
facet
corresponds to for all situations in the description the entity exists
with
a certain property set."

So the "existential facet" is their approach to implementing contexts. 

> Events
> and Actions represent the kinetic portion of the model, 

I don't believe the model has a kinetic portion, that's a term you would
use
when talking about oscillatory systems. Better: "Events and Actions
represent the processes and Situations represent the contexts"?

thanks,

Dr Mark H. Butler
Research Scientist                HP Labs Bristol
mark-h_butler@hp.com
Internet: http://www-uk.hpl.hp.com/people/marbut/
Received on Friday, 6 June 2003 08:23:26 EDT

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