Upon consideration, remove the extensible data

model point in the Summary. Its not supported, and
I cannot think immediately of a need for this. Yes,
it would be nice, but it is not a 'must have'.
Fix up summary points. We were missing point about

missing critical models and refine the point about being
able to create new 'data'-based data models, as it makes
its signficantly harder to achieve solutions to many 'large'
dataset problems.