

 Expert.

 This is an example of a very simple expert system built on top
 of the finite-state machine.  There are only two modifications to
 the basic fsm (in fsm.lisp):

  1. The current time of the fsm is non-monotonically stored in the current context
  (this allows the rules to retrieve the "current state" of the fsm).

  2. There are no "inputs" here and the transitions are triggered by
  rules in the expert system asserting the next state explicitly.

 The states are as follows:

   Diagnosing -> Testing -> Prescribing
       ^            |
       |            |
       --------------

 In this simple example, each state fires rules to fill a given slot
 and then passes control to the next state.

