Set subclasses

Hi Bill:

I wanted to run this question by you because its sort of skewing my
understanding of the Set class heirarchy:

     Why is there a field "ManifoldDimension" in a SimpleSet?

    To ask that in a more roundabout way:

    The definition of the Set class more or less corresponds to my idea of a
set. When I get to SimpleSet, though, and you add the idea of a manifold
dimension, it seems you are defining a manifold. If I use the simple
definition of manifold as "a subset of Rn, along with an invertable and
differentiable function phi:Rm -> Rn", then are you adding the function phi
to the class SimpleSet?

   When I examine the subclasses of SimpleSet, it seems that GriddedSet and
its subclasses define phi in the gridToValue() method.  DoubleSet, FloatSet,
and List1DSet all seem to just be plain sets.