001 package aima.basic.vaccum;
002
003 import java.util.Set;
004
005 import aima.basic.Agent;
006 import aima.basic.AgentProgram;
007 import aima.basic.ObjectWithDynamicAttributes;
008 import aima.basic.Percept;
009 import aima.basic.simplerule.Rule;
010
011 /**
012 * Artificial Intelligence A Modern Approach (2nd Edition): Figure 2.12, page 49.
013 * <code>
014 * function REFLEX-AGENT-WITH-STATE(percept) returns an action
015 * static state, a description of the current world state
016 * rules, a set of condition-action rules
017 * action, the most recent action, initially none
018 *
019 * state <- UPDATE-STATE(state, action, percept)
020 * rule <- RULE-MATCH(state, rules)
021 * action <- RULE-ACTION(rule)
022 * return action
023 * </code>
024 * Figure 2.12 A model-based reflex agent. It keeps track of the current state of the world
025 * using an internal model. It then chooses an action in the same way as the reflex agent.
026 */
027
028 /**
029 * @author Ciaran O'Reilly
030 *
031 */
032 public abstract class ReflexAgentWithStateProgram extends AgentProgram {
033 //
034 // static state, a description of the current world state
035 private ObjectWithDynamicAttributes state = null;
036
037 // rules, a set of condition-action rules
038 private Set<Rule> rules = null;
039
040 // action, the most recent action, initially none
041 private String action = null;
042
043 public ReflexAgentWithStateProgram() {
044 init();
045 // Implementors of the init() method should have ensured the state and
046 // rules are setup
047 assert (null != state);
048 assert (null != rules);
049 }
050
051 public void setState(ObjectWithDynamicAttributes aState) {
052 state = aState;
053 }
054
055 public void setRules(Set<Rule> aRuleSet) {
056 rules = aRuleSet;
057 }
058
059 // function REFLEX-AGENT-WITH-STATE(percept) returns an action
060 @Override
061 public String execute(Percept percept) {
062 // state <- UPDATE-STATE(state, action, percept)
063 state = updateState(state, action, percept);
064 // rule <- RULE-MATCH(state, rules)
065 Rule rule = ruleMatch(state, rules);
066 // action <- RULE-ACTION(rule)
067 action = ruleAction(rule);
068 // return action
069 return action;
070 }
071
072 //
073 // PROTECTED METHODS
074 //
075
076 /**
077 * Realizations of this class should implement the init() method so that it
078 * calls the setState() and setRules() method.
079 */
080 protected abstract void init();
081
082 protected abstract ObjectWithDynamicAttributes updateState(
083 ObjectWithDynamicAttributes envState, String anAction,
084 Percept percept);
085
086 protected Rule ruleMatch(ObjectWithDynamicAttributes envState,
087 Set<Rule> rulesSet) {
088 for (Rule r : rulesSet) {
089 if (r.evaluate(envState)) {
090 return r;
091 }
092 }
093 return null;
094 }
095
096 protected String ruleAction(Rule r) {
097 return null == r ? Agent.NO_OP : r.getAction();
098 }
099 }