Added a sequential, fixed-horizon meta encoding.

encodings/sequential-horizon.lp

@@ -0,0 +1,36 @@
+#const horizon=1.
+
+% Check feature requirements
+:- requires(feature(actionCosts)).
+:- requires(feature(axiomRules)).
+:- requires(feature(conditionalEffects)).
+
+% Horizon, must be defined externally
+time(0..horizon).
+
+% Establish initial state
+holds(Variable, Value, 0) :- initialState(Variable, Value).
+
+% Perform actions
+1 {occurs(Action, T) : action(Action)} 1 :- time(T), T > 0.
+
+% Check preconditions
+:- occurs(Action, T), precondition(Action, Variable, Value), not holds(Variable, Value, T - 1), time(T), time(T - 1).
+
+% Apply effects
+caused(Variable, Value, T) :- occurs(Action, T), postcondition(Action, _, Variable, Value).
+modified(Variable, T) :- caused(Variable, Value, T).
+
+holds(Variable, Value, T) :- caused(Variable, Value, T), time(T).
+holds(Variable, Value, T) :- holds(Variable, Value, T - 1), not modified(Variable, T), time(T), time(T - 1).
+
+% Check that variables have unique values
+:- variable(Variable), not 1 {holds(Variable, Value, T) : contains(Variable, Value)} 1, time(T).
+
+% Check mutexes
+:- mutexGroup(MutexGroup), not {holds(Variable, Value, T) : contains(MutexGroup, Variable, Value)} 1, time(T).
+
+% Verify that goal is met
+:- goal(Variable, Value), not holds(Variable, Value, horizon).
+
+#show occurs/2.