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This example concerns the step in reduction-to-clausal-form involving
reducing the scope of negation.  This example shows that
if you perform some of these steps before others, you will
perform unnecessary steps.  However, you will eventually
get the right answer, regardless of the order in which
you apply them.

Here are several conversions of sentence S:

S. not (ls(john) ->  (not (exists Z (have(john,Z) & mouse(Z))))).
not (not ls(john) or (not (exists Z (have(john,Z) & mouse(Z))))). CHOICE HERE
not (not ls(john) or (all Z not (have(john,Z) & mouse(Z)))).  CHOICE HERE
not (not ls(john) or (all Z (not have(john,Z) or not mouse(Z)))).
ls(john) & not (all Z (not have(john,Z) or not mouse(Z))).
ls(john) & (exists Z not (not have(john,Z) or not mouse(Z))).
ls(john) & exists Z (have(john,Z) & mouse(Z))).
ls(john) & have(john,c22) & mouse(c22)).  3 CLAUSES
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S. not (ls(john) ->  (not (exists Z (have(john,Z) & mouse(Z))))).
not (not ls(john) or (not (exists Z (have(john,Z) & mouse(Z))))). SAME CHOICE 
not (not ls(john) or (all Z not (have(john,Z) & mouse(Z)))).  OTHER CHOICE
not (not ls(john) or (all Z not (have(john,Z) & mouse(Z)))). 
ls(john) & not (all Z not (have(john,Z) & mouse(Z)))).  CHOICE HERE
ls(john) & not (all Z (not have(john,Z) or not mouse(Z))).  CHOICE HERE
ls(john) & exists Z not (not have(john,Z) or not mouse(Z))).  CHOICE HERE
ls(john) & exists Z (have(john,Z) & mouse(Z)).  
ls(john) & have(john,c22) & mouse(c22).    3 CLAUSES
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SHORTEST PROCESS:  work on outer scopes first
S. not (ls(john) ->  (not (exists Z (have(john,Z) & mouse(Z))))).
not (not ls(john) or (not (exists Z (have(john,Z) & mouse(Z))))). CHOICE HERE
ls(john) &  (exists Z (have(john,Z) & mouse(Z))).
ls(john) & have(john,c22) & mouse(c22).  3 CLAUSES
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all X (studyHard(X) and prepareInAdvance(X)) -> (succeed(X) and not worry(X)).
a) Replace A --> B by ~A or B
all X ~(studyHard(X) and prepareInAdvance(X)) or (succeed(X) and ~worry(X)).
b) Move ~ inwards
all X (~studyHard(X) or ~prepareInAdvance(X)) or (succeed(X) and ~worry(X)).
c) Standardize variables
d) Skolemize
e) Drop universal quantifiers
(~studyHard(X) or ~prepareInAdvance(X)) or (succeed(X) and ~worry(X)).
f) Distributive law
(~studyHard(X) or ~prepareInAdvance(X) or succeed(X)) and 
(~studyHard(X) or ~prepareInAdvance(X) and ~worry(X)).
g) Create separate clause for each conjunct
~studyHard(X) or ~prepareInAdvance(X) or succeed(X).
~studyHard(X) or ~prepareInAdvance(X) or ~worry(X).
h) Standardize apart so same variable doesn’t appear in 2 clauses
~studyHard(X) or ~prepareInAdvance(X) or succeed(X).
~studyHard(Y) or ~prepareInAdvance(Y) or ~worry(Y).