The input to a prestrategy is a set of equations *C*.

- S0. Set (see §).
- S1. Run NCProcess1 which creates a display of the output (see O1-O5 in §) and look at the list of equations involving only one unknown (say a particular equation has exactly one unknown ).
- S2. The user must now make a decision about equations in (e.g., is a Ricatti equation so I shall not try to simplify it, but leave it for Matlab). Now the user declares the unknown to be known. The user would also select the equation as important. User selecting an equation corresponds to adding it to the set .
- S3. Either do the ``End game''
(see
§) or Go to S1.

The above listing is, in fact, a statement of a
*1-prestrategy*.
Sometimes one needs a *2-prestrategy* in that the
key is equations in 1 and 2 unknowns.

Another point is that the user can select certain equations which he deems important. The NCProcess commands give these priority over subsequent equations when eliminating unknowns.

The point is to isolate and to minimize what the user must do. This is the crux of a prestrategy.

Wed Jul 3 10:27:42 PDT 1996