W3C home > Mailing lists > Public > public-prov-wg@w3.org > June 2011

RE: PROV-ISSUE-8: defining generation in terms of `IVPT of'

From: Myers, Jim <MYERSJ4@rpi.edu>
Date: Fri, 10 Jun 2011 09:28:41 -0400
Message-ID: <B7376F3FB29F7E42A510EB5026D99EF205286CC6@troy-be-ex2.win.rpi.edu>
To: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
CC: <public-prov-wg@w3c.org>


> -----Original Message-----
> From: Luc Moreau [mailto:L.Moreau@ecs.soton.ac.uk]
> Sent: Friday, June 10, 2011 3:26 AM
> To: Myers, Jim
> Cc: public-prov-wg@w3c.org
> Subject: Re: PROV-ISSUE-8: defining generation in terms of `IVPT of'
> 
> Hi Jim,
> 
> I had not seen your comment in line, my responses are also inline.
> 
> On 10/06/11 02:28, Myers, Jim wrote:
> > This would mean that a heating process modifies an egg to create a
warm egg,
> it does not transform a cold egg into a warm egg?
> >
> > Or do you mean both - a process execution can turn one thing into
another,
> these things can be considered IVPTs of a thing that participates in
the process
> execution/ is modified by the process execution? And in an open world
> assumption, a witness doesn't have to report the modified thing or can
decline
> to identify/report either of things in IVPT roles depending on their
ability to
> observe and the use case they wish to enable?
> >
> > ________________________________
> >
> > From: public-prov-wg-request@w3.org on behalf of Luc Moreau
> > Sent: Thu 6/9/2011 6:44 PM
> > To: Provenance Working Group WG
> > Subject: PROV-ISSUE-8: defining generation in terms of `IVPT of'
> >
> >
> >
> > Hi all,
> >
> > - if a new thing is created, it is clear that we have a new IVPT of
> > that thing
> >
> > if a chicken creates an egg is it just an IVPT of an egg?
> >
> 
> I would think the physical object is the egg.
> I thought we had agreed that for a provenance purpose, we had to talk
about
> an IVPT of that egg.

But 'the egg' is also an IVPT of the stuff that goes into the cake - a
temporary 'state' in which yolk and white are together and not
mixed/chemically altered, etc. 
> 
> > - if the thing is modified, then it is a requirement that a new view
(IVPT) is
> generated ...
> >         otherwise, it would still be a view that existed before
> >
> > can't I say the egg was heated without reporting its cold and warm
states? I.e.
> don't we want to be able to report that something was modified without
having
> to report the IVPTs? A document was edited four times by different
people but I
> don't wan't to/can't tell you what each wrote at each stage?
> >
> 
> These comments were made in the context of defining Generation of an
IVPT.

OK - but you said "if the thing is modified"... For generation, I would
say the chicken participates in an egg laying process execution that
generates an 'egg'. That 'egg' is an IVPT of the chemicals in it (which
existed before). The 'egg' can also have further/more stateful IVPTs
that are more useful for discussing heating, cracking, etc. The sense in
which generation is special is that it is a derivation from things we
don't consider logically an aspect/IVPT of something greater. I.e. the
'mass of egg-bound chemicals' in the chicken just changes its state to
become the 'egg', nothing really appears or disappears (conservation of
mass and energy). Unless/until a scientist wants to look at the
potential for different processing of chemicals going into the egg
versus those used to build the chicken's own body, 'mass of egg-bound
chemicals' isn't something we'd usually think about, but it's a valid
perspective and consistent with the view of an egg being generated (both
views can be drawn on the same graph in the way I've been describing).

> 
> The document was edited four times could be expressed by 4 process
execution
> and something like opm:wasTriggeredBy in between.
> 
> > - if the process execution was taking a long time to modify/create
the thing,
> there is only one
> >     instant at which the (invariant!) IVPT appears
> >
> > I thnk we could define it that way, but if a cracking process takes
time, saying
> the cracked egg appears instantaneously basically means you want
'cracked egg'
> to be defined by some threshold - the cracked egg might become more
cracked
> over time ) invariant only in that it is always above the threshold
and the
> instance of the creation of the IVPT relationship occurs ata
aspecific instant.
> >
> 
> Yes, agreed.
> 
> > - I think this captures well a stateful objects, where processes can
modify the
> object, resulting in
> >     different IVPTs corresponding to the various states
> >
> > IVPTs are not a separate kind of thing and their invariance is
relative. If they
> are truly immutable sates/snapshopts, they can only exist for an
instant because
> some part of the state of the thing (a part we may not care about such
as age)
> will change immediately.
> >
> I am not sure I agree, here. IVPTs are a view/perspective on a thing.

Perhaps I should argue from the other direction - the notion of a thing
is also a perspective/view. "eggs" don't exist - only temporary
co-locations of particular molecules. Galton and Mizoguchi's paper
argues that objects are defined by what processes you consider to be
internal to and external to the object - if you change the set of
processes you are concerned about, you describe the world using
different objects. In this sense, eggs feel more 'real' because the set
of processes we see happening frequently to them preserve aspects of
their state, so egg as an IVPT is useful/predictive/etc. 
> 
> Alternative views asserted by other asserters may co-exit.
> - it's a decaying egg
> - it's a duck egg, not a hen egg
> - it's a chocolate egg
> 
I agree, so again from the other direction - I don't see why 'egg' is
more real/more correct/more special than any of these, they're all
IVPTs.

> It is a requirement of any specific perspective to be invariant.

Invariant relative to a view in which only certain processes are of
interest (are observable/reported?).

> So, it's not a snapshot of the global egg state, but it's a snapshot
according to a
> view.
> 
> An analogy would be several cameras pointing to a same egg.
>  From one camera, the egg is still, no change occurring.
>  From the other, we see a crack appearing.
> So one asserter can describe change in a physical object, while
another does not
> describe any change.
> But it's the same egg.

Right - those are two views of something. But that something is just
another view - one camera sees a soup of chemicals that are swirling and
mixing (slowly for an egg) while another sees one thing (the egg). Both
of these are just IVPTs too. The chemical view is mutable by more
processes than the egg view, but it is more persistent (it lasts longer
because we've defined it in a way that the processes that can
create/destroy it are less frequent).

I know that thinking of everything as an IVPT is not necessarily
intuitive, and that one can argue that it is just one way to model the
world/a philosophy, but I think it is a model that has the right
conceptual power to deal with the use cases we have (and the general set
we can envision) while also being one that, in practice, will fade away
- most people will agree that 'egg' and not 'mass of chemicals' is a
more useful IVPT to talk about and we'll see 'eggs' used in cake baking
and the world will mostly look like OPM (straight thing-execution-thing
chains), but we'll still have the power to drop down and talk about
cracking or go up and talk about conservation of mass when needed.

I also don't know what a coherent alternative is that, once we add in
all the features necessary to cover the use cases, we'll like better.
There are certainly other ways to model - my question really is whether
there are others that will end up being more intuitive once all the
needed features are dropped in.

-- Jim

 Jim
> 
> Luc
> > What do you think?
> >
> >
> http://www.w3.org/2011/prov/wiki/ConceptGeneration#Definition_of_Gener
> > ation_by_Luc
> >
> > Cheers,
> > Luc
> >
> >
Received on Friday, 10 June 2011 13:29:48 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 13:06:31 GMT