started to develop STRIPS encoding variants

encodings/strips/preprocess.lp

@@ -0,0 +1,48 @@
+% Constant '_closure' to (de)activate analysis of potentially relevant actions
+% - value '1': forward chaining of effects w.r.t. initial variable values
+% - value '2': backward regression of effects w.r.t. goal variable values
+% - value '3': both forward chaining and backward regression of effects
+% - otherwise: off
+
+#const _closure = 3.
+
+% Check feature requirements
+
+:- requires(feature(actionCosts)).
+:- requires(feature(axiomRules)).
+:- requires(feature(conditionalEffects)).
+
+% Basic redundancy check for actions
+
+postcondition(A,X,V) :- postcondition(A,E,X,V).
+
+has_condition(A,X,0) :- action(A), precondition(A,X,V).
+has_condition(A,X,1) :- action(A), postcondition(A,X,V).
+
+inconsistent(A) :- has_condition(A,X,P),
+                   #count{V : precondition(A,X,V), P = 0;
+                          V : postcondition(A,X,V), P = 1} > 1.
+consistent(A)   :- action(A), not inconsistent(A).
+irredundant(A)  :- consistent(A), postcondition(A,X,V), not precondition(A,X,V).
+
+% Forward chaining of effects w.r.t. initial variable values
+
+feasible(X,V) :- initialState(X,V).
+feasible(X,V) :- possible(A), postcondition(A,X,V).
+
+possible(A) :- irredundant(A), feasible(X,V) : precondition(A,X,V).
+possible(A) :- irredundant(A), _closure != 1, _closure != 3.
+
+:- goal(X,V), not feasible(X,V).
+
+% Backward regression of effects w.r.t. goal variable values
+
+produce(X,V) :- goal(X,V), not initialState(X,V).
+produce(X,V) :- active(A), precondition(A,X,V), not initialState(X,V).
+produce(X,V) :- persist(X,V), active(A), has_condition(A,X,1), not postcondition(A,X,V).
+
+persist(X,V) :- goal(X,V), initialState(X,V).
+persist(X,V) :- active(A), precondition(A,X,V), initialState(X,V).
+
+active(A) :- possible(A), postcondition(A,X,V), produce(X,V).
+active(A) :- possible(A), _closure != 2, _closure != 3.