RE: Aside - Re: Question: DAML cardinality restrictions

> From: Jan Grant [mailto:Jan.Grant@bristol.ac.uk]
[DAML examples elided]
> I can't help feeling a little worried by these examples. Yes, I know
> they're "only" examples. But the model of the world they present is
> broken - will DAML be good for describing the real world or just
> mathematical arenas and EDI? Is it even wise to try the former - or
> should the examples be rewritten to be less contentious?

Probably, but I think there are problems when entirely removing contention
from examples such as these.

[Sanity warning: these ideas are no doubt unfinished, and are contributed so
that people with much more experience than me can bat them around some more
or tell me where the answers are]

One problem as a language or formalism designer is that it's very difficult
to use the thing until you've written it, and examples tend to be dreamed up
on the spur of the moment and then stick.  With SMK and GRAIL, for example,
we were fond of using "compound composite fracture of the left humerus" (or
"compound fracture of the middle eyebrow" to illustrate what could happen
without constraints).  These examples do tend to take on a life of their
own, and are frequently in entirely arbitrary domains because it's easier to
talk about than naming the concepts Cn, the roles Rn, and the datatypes Tn.
So one source of contention is simply that there are more useful things to
spend time on (from the designer's point of view :-).  This can be reduced
by the designers expending more effort on the examples, but the third and
fourth categories of contention (below) may then creep in.

A second problem, especially for concrete datatypes, is the unit problem.
What do you measure shoe size in?  Inches?  Abstract units (see below)?  Is
that speed in miles per hour, kilometres per hour, metres per second, or
furlongs per fortnight?  So a second source of contention is from
underspecified examples; this can be reduced by being more explicit about
your units, but I don't see anything in XML Schema that aids this [a pet
peeve of mine].

A third and more subtle problem is assumptions that standards are the same
worldwide.  Is that abstract unit representing shoe size UK/US/Japan, male
or female?  So a third source of contention is implicit localisation; this
can be reduced by describing mathematical arenas and EDI, by sufficient
experience on the part of the modeller to know that differences exist, or by
the whole world standardising on the same units :-).

A fourth problem (well-known to many of the list members) is that defining
an ontology may make explicit the assumptions of the team creating the
model, and those assumptions may not be universally applicable.  Not
everyone wears shoes, or even has legs.  A travel ontology may include names
of countries; what do you do when there are named regions that are not
universally recognised as independent nation states?  How do you model the
ownership of the West Bank?  And what happens when organisations that would
naturally have differing views aim to use the same ontology?  So a fourth
source of contention may be experience or ideology; this can also be reduced
by describing mathematical arenas and EDI.

I think the least contentious models would therefore be those that described
universally agreed areas that have an existing formal definition in another
form --- maths and products (excepting units) seem to fit well here.
Descriptions of the real world are always filtered through the perceptions
and models of the describer; DAML certainly seems capable of acting as a
notation for those descriptions, but I think much of the description will
have to come from the people requiring the descriptions rather than those
defining the notation.

		- Peter

Received on Friday, 30 March 2001 06:55:04 UTC