Re: DAML-S expressiveness challenge #2

David Martin wrote: 
> In a DAML-S process description, we need to be able to express the
> following sort of restriction:
>   the set of things whose property P has values in [C1, C2,...CN]
> that is,
>     the set of things x such that, for each property instance P(x, y), y
> is a daml:list whose first element is an instance of C1, second
> element an instance of C2, ..., and nth element is an instance of CN.

Does it have to be a daml:list and is N fixed?  If it doesn't have
to be a list and if we know what N is for each use, an easy solution would
be to restrict values to a new class that has a named, restricted
property for each of the list elements.  To capture the ordering that
is inherent in a list, the properties could be named 1st, 2nd,
3rd, 4th, 5th, 6th ... with the obvious interpretation. We'd also need 
to assume (probably) that N is never greater, in practice, than some 
upper limit (e.g. 20).

I guess this would be like creating special classes to represent the lists
of lengths from 1 to 20.  We could call them 1List, 2List, 3List, ... 20List.
Each of these could then be specialized, as needed, by attaching restrictions 
to the ranges of their named elements.

--
 Tim Finin, Prof Computer Science & Elect Eng, Director Inst. for Global
 Electronic Commerce, Univ of Maryland Baltimore Cty, 1000 Hilltop, Baltimore
 MD 21250. 410-455-3522 fax:-3969 finin@umbc.edu http://umbc.edu/~finin/