DENDRAL Meeting JUN 2 3 1989
June 11, 1969

Lederberg,Fei genbaum,Duffield,

Schrol1,Bersohn, Delfino, Buchanan

4%
1. Rings -- Bersohn's proposal,much like previous work which
comes to difficulties which the Hamiltonian circuit approach
is designed to avoid.

2. Inference Rules from Predictor Theory -- two approaches
i) From the behavior of the predictor
ii) From the rules of the predictor, the theory itself,

Best to use (ii) if possible, then test with (i).

3. Problem Solving in the DENDRAL Space
Question: How canf the structure generator tailor-make
hypotheses in light of the data and the xgkawyR theory?

Lederberg's suggestion:

a) Call the predictor during structure generation to judge
the plausibility of a radical. Alternatively, do this
for each of the radicals in the dictionary at the start.

b) Save the current state of Goodlést. (EF.e., make
Goodlist a list of previous states plus the current state.)

c) At the top of Goodhkist put the radicals which seem most
plausible at the moment, taking others off which no longer
seem likely In light of the data.

d) Check to see that you have not used this new state of
Goodlist, by checking through the list of previous states.
This ts necessary to avoid looping. wagausa We may not
want the structure generator to finish a branch before
Goodlist is revised, however, in which case the program
is not necessarily in a loop if we reenter with some
previously used Goodlist.

e) Generate structures, looping xa back to (a) when
appropriate.

Other suggestions for efficient use of this staategy:
a) If there is a dictionary, use the predictor on each
iten initially to put radicals on Goodlist.
b) If the compcsition has only one heteroatom, make that
atom bhe center of the structure.
c) Put superatoms at the center of structures.
d) Let the theory guide structure ganeration by look-ahead
pm as in chess. £E.g., Should the next node be a heteroatom?
If yes, then take the current superatom off (the top level
of) Goodlist, attach the heteroatom to it and put the
new superatom on Goddlist.