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At 11:45 AM -0400 3/12/08, Patrick Cassidy wrote:
Matthew,
There are some points I think are
worth pursuing:
[PC] > > We know how to
resolve terminology
> > clashes - use different names or different namespaces for
the
> > different concepts.
>
> MW: That is not true for 3D/4D, it is about what sorts of
things
> physical objects (in particular) are. For a 4-dimensionalist
they
> are extended in time and have temporal parts, for a 3
Dimensionalist
> they wholly exist now, pass through time, and do not have
temporal
> parts. The terminology is frankly irrelevant, it is the ideas
that
> are diametrically opposed.
As I have mentioned before, I believe that 3D and 4D are
different and
compatible views of the same entities.
Here is the heart of the issue, I believe. Yes, in a sense of
course this is correct. There are things in the actual world which
everyone agrees we are all are talking about: people, events,
timeperiods and so on. Nobody is disagreeing about that. So if these
actual, real things are your 'entities' (as they probably are for the
editors of Longmans) then we are all talking about the same things.
However, to say this is not to say that we all conceptualize
this one reality in the same way, or still less that only one
conceptualization is possible, or that we will all come to agree on
one. In fact, it is close to provable that more than one
conceptualization is possible. (I say 'close to' because the
possibility remains that if enough work were done, the alternatives
might turn out to be isomorphic in a strong enough sense, just mapped
to philosophical words differently: but I doubt this, myself, as
deeper analysis never seems to converge to conceptual
agreement.)
We can use different words to
describe our views, but the important question for the machines is
whether
the different views lead to *representations* that are logically
inconsistent.
Well yes, they do. And in fact the representations seem to come
first: the words have been invented as terms of art in order to
explain the conceptualizations.
We don't need to agree on which
aspect of the entity is of
greatest importance to us
Everyone is agreed on that point.
- we have to agree on how to represent
those
different views, optimally in a way that can be related and not be
logically
inconsistent. I presented an example in a previous post in this
thread of
how one 3D view can be reconciled with one 4D view. If you think
there are
4d and 3D views that are logically inconsistent, please show us the
axioms
that lead to inconsistency.
To say
(1) extended in time and have temporal
parts or
(2) wholly exist now, pass through
time, and do not have temporal
parts
Is to describe two different views of the same
object.
Yes, in a sense: but its those 'views' that get described by the
ontologies, not the objects themselves. And if two people have
divergent such views, and each think the other's view incoherent,
neither of them is going to be happy with a third view which
manages to reconcile them. Part of the basic assumption of each
ontology are axioms which explicitly deny (or which make
syntactically illegal) basic assumptions of the other.
The task of
ontological engineering is not to describe the ultimate structure
of
reality, but to create a representation that is useful for
automated
inferencing in solving practical problems. The only thing
relevant is how
these views are formalized. It can be helpful for people using
the ontology
to have good documentation as well - the documentation can include
the
different interpretations. The issue is whether the
formalizations are
inconsistent.
[[[3]]]
[MW] > MW: Yes, you could put both 3D and 4D theories into some
ontology
> repository, and provide a mapping between them. This is quite
possible.
> But make no mistake, you now already have a lattice of theories
and
> two foundation ontologies, not one.
Each physical object would be
> represented twice, once as a 3D object and once as a 4D
object
No, you would not have two ontologies, you would have one
self-consistent
ontology in which two different and compatible views are represented,
with
axioms that automatically convert an
assertion in one form into the
equivalent assertion in the other form.
Well, that's a point of view, and I applaud it myself: but to
phrase Matthew's point slightly differently: make no mistake, some of
the users of your ontology will vehemently object to some of the
inferences it makes, regarding them as philosophical errors or worse,
and your ontology, even if it is self-consistent internally, will not
be consistent with other ontologies that these folk prefer to use. So
you will have to do the inter-ontology mappings that you are trying to
avoid in any case, in order to achieve interoperability across
communities.
One could, of course, create
subontologies in which either of the forms is represented without the
other.
But these will be logically compatible, and any time assertions in the
two
subontologies need to be related, they can be converted
accurately.
Actually it goes only in one direction, as the 4-d framework is
more expressive than the continuant/occurrent framework, and can 'say'
things that are incoherent or impossible in the other.
In the
full ontology, one might very well have two different representations
of the
same entity, but they would be created automatically and accurately
from a
single assertion in either form (4D or 3D), and would not change the
effects
of the inferencing.
Sure they would. They increase the size of the search space. Read
Barry's posts to the ontolog thread on 'orthogonality'.
Fear of redundancy is one of the
factors that has
inhibited creation of such an inclusive ontology. I do not
believe it is a
problem, because utilities can be created to allow users to select
only the
parts they need from the full ontology, and in that way the redundancy
will
have no effect on performance in stand-alone
applications.
Again, I applaud this idea, but the technical issues involved are
essentially the same as those involved in describing mappings between
ontologies. Its the same problem in a different terminology. And
having all this in one large ontology puts extra strain on the logical
language: it has a lot more to express. (This is why Cyc adopted
'micro-theories' to try to keep track of all the relationships between
sub-ontologies. Terms change their meanings in different ontologies,
for example.)
When the full
ontology is used to enable interoperability between two views, the
inferencing may be slower. How much slower will be discovered in
practice.
[[[4]]] [MW] >> MW: Just take a close look at what Pat H is
saying about the
> incompatibility between 3D and 4D.
>
I did, and I was astonished to see him produce a set of assertions in
which
the '=' sign is used (it appears to me) in two different
senses
OK, if that example bothers you (and I agree it is somewhat
tendentious), try this, which makes the same basic point but more
realistically, and is therefore more complicated.
First, a fragment of a continuant/occurrent ontology, such as
DOLCE. Here, the categories of Occurrent and Continuant (think process
and object respectively) are firmly and without exception asserted to
be disjoint. One can speak of temporal parts of an occurrent by
using during:
(during O t) is the temporal part of the occurrent O at the time
t. Occurrents however cannot have temporal parts, so one would use
fluent language to speak of a changing property of a continuant:
(P c t) rather than (P (during c t)). It would be natural to have
a domain axiom for during:
(forall (x)(if (exist (y (t Time))(= y (during x t))) (Occurrent
x) ))
Ie if something has a temporal part, then its an Occurent, from
which it follows in this ontology that it is not a Continuant. {Note:
this axiom as written would not do the job in CLIF, in fact, as all
functions there are total. See the IKL Guide document for more details
on how to do this properly, which I omit here for the sake of
simplicity.} And certainly in this ontology, continuants exist: they
are a central category, so for example we might have
(Continuant PatHayes)
OK, now turn to a '4-d' ontology. Here, all spatiotemporal
entities have temporal parts, and the two forms of _expression_ (P
x t) and (P (x during t)) are completely equivalent, mere
syntactic alternatives:
(forall (x (t Time) P)(iff (P x t)(P (x during t)) ))
Now, how do we put these together? Since the latter is simply
more permissive than the former, we might just try to combine them
directly, but then a contradiction arises whenever the second uses
during on a continuant argument. Or, we could treat the
continuant/occurrent distinction as being real even in the second
ontology, rendering it consistent at the cost (unacceptable to its
users) of making it effectively the same as the first one. Or, we
could weaken the first ontology slightly, by removing the assumption
of disjointness, making it effectively similar to the second one: but
its devotees will object that this change utterly destroys the very
distinction that they are at such pains to preserve, because it is so
fundamental. There is no way to make everyone happy. Or, one can
divide the universe into two sub-universes, one containing 4-d
'things' and the other containing the continuants and occurrents,
restrict each sub-ontology to its part of this enlarged universe, and
proceed: but now the two sub-ontologies are effectively isolated from
one another, and the whole construct is a single ontology only in
name, not in any useful sense. Ther are now two PatHayeses, the
continuant and the 4-d one, and no way in the ontology itself to
even state what the relationship might be between them.
, but is
considered identical for the purpose of inferencing. He has
denied that the
meanings are different
In passing: the equality symbol in CL is part of the logic, so
obviously has the same meaning everywhere.
, and we will soon I expect proceed to
discuss this
point further.
I look forward to it.
Pat
But if that is the best argument
against 3D being compatible
with 4D, I think my case is proven.
Pat
Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-
> bounces@xxxxxxxxxxxxxxxx] On Behalf Of matthew.west@xxxxxxxxx
> Sent: Wednesday, March 12, 2008 10:20 AM
> To: ontolog-forum@xxxxxxxxxxxxxxxx
> Subject: Re: [ontolog-forum] Ontology similarity and accurate
> communication
>
> Dear Pat,
>
> >
> > MW - one request for clarification:
> >
> > [MW] >
> > > MW: I'm afraid I do not agree with Pat C at all. I
have
> > spent much of
> > > my life doing business analaysis for systems design,
and reviewing
> > > data models produced by others. I am always surprised
at just how
> > > different (and usually limited) peoples mental models
are.
> > I have yet
> > > to see two data models of the same application look
the
> > same except by
> > > cut and paste.
> > >
> >
> > I am well aware that models created in isolation from
each
> > other will vary
> > widely. That is a restatement of the problem.
The hypothesis of the
> > 'Conceptual Defining Vocabulary' states that it will be
> > possible to solve
> > that problem with a common ontology of agreed basic
concepts
> > that are used
> > to specify the meanings of the more specialized concepts
in
> > the different
> > models.
>
> MW: I agree it is possible to come up with a common ontology
of
> basic concepts that can be used to integrate the diverse
models
> you talk about. I have done this myself with ISO 15926.
However,
> you are claiming that there is ONE such ontology which we all
> share by some sort of osmosis. The point I was trying to make
> about all the different data models is that there is not such
> ONE ontology. I beleive there are several possible ontologies
with
> different ontological foundations, each of which would be
quite
> capable of helping to integrate diverse other ontologies of
> whatever form.
>
> MW: Further you are claiming that there are a limited set of
> foundation objects from which all others can be defined. This
> also does not sit true with me. I have seen new
primitive
> concepts arise at almost any and
every level of an ontology. I
> agree that it is very useful when classes can be defined as
the
> intersection of some other classes, but it doesn't actually
happen
> that often for me (though I admitedly usually leave these to
> be implied, rather than making them explicit).
>
> MW: Just as a simple example, can you show how you would
move
> from even a relatively general class
like pump, to centrifugal
> pump? Where do you get the centrifugal from?
> >
> > ** The relevant question is, when a group of people
who are
> > determined to
> > find a common model of *basic* concepts get together,
what
> > kinds of issues
> > remain that cannot be resolved by sincere efforts to find
ways to
> > accommodate the needs of all of them? **
>
> MW: My experience again is that whatever you choose, there
will
> be some people who will find it unpalatable enough to walk
away.
> I would certainly not waste my time with anything 3D as an
example,
> and there are others who would not countenance 4D.
> >
> > I am very interested in finding out just what
kinds of
> > residual problems
> > there really are. Thus far the examples I have seen
all resolve to a
> > terminology clash - two different people want to use the
same
> > term to refer
> > to concepts of different meaning. We know how to
resolve terminology
> > clashes - use different names or different namespaces for
the
> > different
> > concepts.
>
> MW: That is not true for 3D/4D, it is about what sorts of
things
> physical objects (in particular) are. For a 4-dimensionalist
they
> are extended in time and have temporal parts, for a 3
Dimensionalist
> they wholly exist now, pass through time, and do not have
temporal
> parts. The terminology is frankly irrelevant, it is the ideas
that
> are diametrically opposed.
>
> > If it is important to relate those concepts to
> > each other, that
> > takes a bit of work to analyze the reasons for the
> > differences and find the
> > relations between the two different representations.
>
> MW: Yes, you could put both 3D and 4D theories into some
ontology
> repository, and provide a mapping between them. This is quite
possible.
> But make no mistake, you now already have a lattice of theories
and
> two foundation ontologies, not one. Each physical object would
be
> represented twice, once as a 3D object and once as a 4D
object.
> >
> > If there is a case where an effort of that kind
could not arrive at
> > agreement on how to include or reconcile some seemingly
logically
> > incompatible representations, I would very much like to
learn
> > what those
> > problems are, in detail.
>
> MW: Just take a close look at what Pat H is saying about the
> incompatibility between 3D and 4D.
> >
> > Pat
> >
> > Patrick Cassidy
> > MICRA, Inc.
> > 908-561-3416
> > cell: 908-565-4053
> > cassidy@xxxxxxxxx
> >
> >
> > > -----Original Message-----
> > > From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-
> > > bounces@xxxxxxxxxxxxxxxx] On Behalf Of
matthew.west@xxxxxxxxx
> > > Sent: Wednesday, March 12, 2008 6:41 AM
> > > To: ontolog-forum@xxxxxxxxxxxxxxxx
> > > Subject: Re: [ontolog-forum] Ontology similarity and
accurate
> > > communication
> > >
> > > Dear John and Pat H.,
> > >
> > > > >In other words, all the axioms are at the task
level, and each
> > > > >message sent between systems identifies what
ontology is
> assumed.
> > > >
> > > > I agree that makes a certain sense, but Im less
sanguine
> > than you are
> > > > about being able to neatly express relationships
between
> > ontologies.
> > > > Not that such relations are impossible, but I
think they
> > will will be
> > > > messier and more tangled, as Mala says in her
recent
> > message. Which
> > > > is not necessarily a problem or something to
avoid, just
> > something we
> > > > should be ready for.
> > >
> > > MW: I agree with Pat here, that just encouraging an
> > unlimited number of
> > > ontologies and saying we will map between them, is
perhaps
> > where we are
> > > headed at the moment, but it is an expensive direction
to
> > take. My best
> > > hope at the moment is to
encourage convergence onto a limited
> number
> > > of ontologies - say 10 or so. They would have clearly
stated
> > > foundations
> > > where the differences would be known and understood,
and
> > mappings could
> > > be provided. I think several is good, because that
provides
> > a market,
> > > which will help to drive improvement. It might also be
that
> > some die,
> > > and others are born.
> > >
> > > MW: I'm afraid I do not agree with Pat C at all. I
have
> > spent much of
> > > my life doing business analaysis for systems design,
and reviewing
> > > data models produced by others. I am always surprised
at just how
> > > different (and usually limited) peoples mental models
are.
> > I have yet
> > > to see two data models of the same application look
the
> > same except by
> > > cut and paste.
> > >
> > > Regards
> > >
> > > Matthew West
> > > Reference Data Architecture and Standards Manager
> > > Shell International Petroleum Company Limited
> > > Registered in England and Wales
> > > Registered number: 621148
> > > Registered office: Shell Centre, London SE1 7NA, United
Kingdom
> > >
> > > Tel: +44 20 7934 4490 Mobile: +44 7796 336538
> > > Email: matthew.west@xxxxxxxxx
> > > http://www.shell.com
> > > http://www.matthew-west.org.uk/
> > >
> > >
> > >
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