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The idea of a prestrategy is :

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

S0. Set tex2html_wrap_inline4764 (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 tex2html_wrap_inline4766 has exactly one unknown tex2html_wrap_inline4248 ).
S2. The user must now make a decision about equations in tex2html_wrap_inline4248 (e.g., tex2html_wrap_inline4766 is a Ricatti equation so I shall not try to simplify it, but leave it for Matlab). Now the user declares the unknown tex2html_wrap_inline4248 to be known. The user would also select the equation tex2html_wrap_inline4766 as important. User selecting an equation corresponds to adding it to the set tex2html_wrap_inline4190 .
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