Definitions of computation have, in the past, been quite restricted. The definitions have been based on arithmetic operations on Boolean values or on the diadic rationals. These definitions have been thought of as models of the digital computers in use today. These models have served useful purposes, but may not be sufficient as a guide for the future.

It appears to be useful to consider the notion of computation in a wider context. Specifically, we should try to include the kind of computation that takes place in neural systems, and what may happen in quantum systems.

We will discuss some recent results in these areas.