12_BChaining.py

knowledge_base = {
    "rule1":{
        "if":["A","B"],
        "then":"C"
    },
    "rule2":{
        "if":["D"],
        "then":"A"
    },
    "rule3":{
        "if":["E"],
        "then":"B"
    },
    "rule4":{
        "if":["F"],
        "then":"D"
    },
    "rule5":{
        "if":["G"],
        "then":"E"
    },
}


def backward_chaining(goal, known_facts):
    if goal in known_facts:
        return True
    for rule, value in knowledge_base.items():
        if goal in value["if"]:
            all_conditions_met = all(condition in known_facts for condition in value["if"])
            if all_conditions_met and backward_chaining(value["then"], known_facts):
                return True
    return False


if __name__ == "__main__":
    goal = "C"
    known_facts = ["G", "D", "E"]

    if backward_chaining(goal, known_facts):
        print(f"The Goal '{goal}' can be reached")
    else:
        print(f"The goal '{goal}' cannot be reached")