/** Helper method for groundedUnify. */
private boolean groundedUnify(APLVar t, SubstList<Term> theta) {
Term subst = theta.get(t.getName());
if (subst != null) return groundedUnify(subst, theta);
else {
theta.put(t.getName(), this);
return true;
}
}
/**
* Selects an applicable PC-rule. A PC-rule is applicable if the head matches the
* event/message/abstract action <code>a</code> and the guard is satisfied by the beliefs of the
* module. Returns a copy of the rule with fresh (unique) variables such that is does not
* interfere with the variables that already occur in the plan from which the abstract action is
* called.
*
* @param beliefbase the beliefs
* @param a the event/message/abstract action
* @param unfreshVars the list variables that cannot be used anymore
* @param theta the substitution for applying the rule
* @return the selected PC-rule
* @throws NoRuleException thrown if no rule is specified for <code>a</code>
*/
public PCrule selectRule(
Beliefbase beliefbase, APLFunction a, ArrayList<String> unfreshVars, SubstList<Term> theta)
throws NoRuleException {
boolean norulefound = true;
for (PCrule pcrule : rules) {
SubstList<Term> theta2 = new SubstList<Term>();
PCrule variant = pcrule.getVariant(unfreshVars);
Query guard = variant.getGuard().clone();
APLFunction head = variant.getHead();
if (a == null) continue; // TODO why???
if (Unifier.unify(head, a.clone(), theta2)) {
norulefound = false;
guard.applySubstitution(theta2);
if (beliefbase.doQuery(guard, theta2)) {
theta.putAll(theta2);
return variant;
}
}
}
if (norulefound) throw new NoRuleException();
return null;
}