Dear John, (01)
> Dear Matthew,
>
> JFS>> I very, very, very strongly doubt that the choice of a 3D vs
> >> 4D upper ontology would have the slightest effect on the design
> >> of a database for airline schedules, train schedules, and many
> >> similar applications.
>
> MW> It is precisely when you deal with times and places (individuals
> > in general) that you get distinctly different results. I have not
> > modelled the specific examples above, but I have done similar
> > things that are Oil Industry related.
>
> I agree that the interpretation of what a flight "really" is would
> be different in a 4D or a 3D ontology, but a low-level fact such
> as the following would not change:
>
> Flight: American Airlines fl 2916 (on Boeing 767-300)
> Depart: 11:30 AM, San Francisco, CA (SFO)
> Arrive: 07:59 PM, New York, NY (JFK)
>
> The airlines have been storing such information in their databases
> for over 40 years without having a detailed ontology about the nature
> of places, times, things, and events. A knowledge base can interpret
> that data with 4D axioms while sending and receiving messages about
> the data to and from knowledge bases and data bases with very
> different upper-level axioms or no such axioms at all. (02)
MW: Oh, of course, they have been holding the data for decades, and
fixing up/misusing data structures to do what they need. But that is
not the same as saying they have been using a 4-D data model to do it,
or as you say something with any explicit ontological foundation. And
since the data is adequate it is possible to map that to a 4-D model. (03)
MW: But that is quite different from it *being* a 4D model just because
it holds the necessary data.
>
> MW> However, this did remind me of what I thought could be shared
> > in lower level modules, and that is the sort of stuff that says
> > things like "centrifugal pumps have impellers as parts". These
> > kinds of statements at a class level I think it may be possible
> > to merge with either a 3D or 4D foundation. When you merge it
> > with a 3D foundation you allow classes to change their membership
> > over time, when you merge it with 4D ontollogies they become
> > extensional.
>
> I agree. Note that AA 2916 uses a B767-300 airplane, but nothing
> in that data depends on the nature of any airplane of any kind.
> The only relevant information about the type B767-300 is the
> number of parts of type Seat and their locations in the aircraft.
> Two computers can interoperate on airline reservations if they
> agree on that level. Their upper ontologies are irrelevant. (04)
MW: The problem is knowing which data of this sort is actually
independent of the upper ontology (i.e. it morphs when moved from
one to the other).
>
> MW> It is not clear to me for how much stuff this would work, but
> > I do think it is worth pursuing to see where the boundaries lie.
>
> My claim is that interoperability is always at the message level
> for agents of any kind -- computer or human. There is no need
> to align their global ontologies. (05)
MW: Ultimately, this is always true. Though ontology is also relevant
to the systems that interoperate. The problem here is the spaghetti
problem of having to deliver pairwise interfaces. So even though
you do not in practice get n**2 interfaces to sort out, you still get
a lot more than the n you get from making a hub with a shared ontology
and interfacing through that hub. It is not only about what is ultimately
possible, it is about what is economically worthwhile. And you won't have
to go far to find someone to tell you that maintaining interfaces has
a high cost, because they change when the system at either end changes. (06)
MW: I wrote a paper about this on an architecture to support large
scale integration a few years ago.
http://www.matthew-west.org.uk/Documents/IIDEASforPDTEurope.pdf (07)
MW: As you suggest this leaves the ontologies of the applications you
wish to integrate untouched, but integrates them with a hub and spoke
mapping to a single hub ontology, rather than multiple point to point
messages, each with any or no ontology. (08)
MW: This work has also been standardised as ISO 18876 parts 1 & 2
Integration of Industrial Data for Exchange Access and Sharing (IIDEAS).
>
> If anyone has any evidence to the contrary, I would love to see it. (09)
MW: The evidence is not about theory, but about economics.
>
> John
>
>
>
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