Default unification: online vs. offline

Rob Malouf malouf at let.rug.nl
Wed Oct 24 09:07:43 UTC 2001


Hi,

>   Apparently, YADU (L&C 1999) can manage pretty well with default
> unification, however it doesn't provide a good solution to deal with a
>   multi-dimensional type hierarchy.

Perhaps if Alex or Ann is following this they should jump in here, but I'm
pretty sure that YADU works just fine with a multi-dimensional type
hierarchy. In the case where conflicting default constraints are inherited
from orthogonal dimensions of the hierarchy, the result is the generalization
of the conflicting constraints. For example, in a Nixon diamond, where
something inherits the constraint [ F / a ] (i.e., the value of the feature F
is, by default, an object of type a) from one dimension and the constraint
[F / b ] from another orthogonal dimension, the effect will be that the value
of F will be constrained to be the least upper bound of a and b. It's true
that strictly speaking constraints can't be overridden by conflicting
constraints from an orthogonal dimension, but the result is certainly
well-defined and, in my opinion at least, pretty much what you want. Or is
there some other problem you had in mind?

------------------------------------------------------------------------------
Rob Malouf                       Alfa-Informatica, Rijksuniversiteit Groningen
malouf at let.rug.nl                                http://www.let.rug.nl/~malouf



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