人工智慧 -- 邏輯推論引擎實作 (Java)
import java.util.*;

class BooleanLogic {
    Random random = new Random();

    public static void main(String[] args) {
        String rules = "a<-b,c;b<-d,e;c<-d,f;d;e;f";
        hornReasoning(rules.split(";"));
        unitResolution(rules.split(";"));
    }

    public static String neg(String pTerm) {
        if (pTerm.startsWith("-"))
            return pTerm.substring(1);
        else
            return "-"+pTerm;
    }

    public static String rewrite(String rule) {
        StringBuffer rzRule = new StringBuffer();
        String head = STR.head(rule, "<-");
        String body = STR.tail(rule, "<-");
        rzRule.append(head);
        if (body.length() > 0) {        
            String[] conds = body.split(",");
            for (int i=0; i<conds.length; i++)
                rzRule.append(","+neg(conds[i]));
        }
        return rzRule.toString();
    }

    public static void unitResolution(String[] pRules) {
        Vector rules = new Vector();
        for (int ri=0; ri<pRules.length; ri++)
            rules.add(rewrite(pRules[ri]));
        for (int ri=0; ri<rules.size(); ri++) {
            String rule1 = (String) rules.get(ri);
            if (rule1.indexOf(",")>0) continue; // it's not unit rule.
            String term = rule1;
            String negTerm = neg(term);
            for (int rj=0; rj<rules.size(); rj++) {
                String rule2 = (String) rules.get(rj);
                String exp = ","+rule2+",";
                if (exp.indexOf(","+negTerm+",")>0) {
                    String unifyExp = STR.replace(exp, ","+negTerm+",", ",");
                    String newRule = unifyExp.substring(1, unifyExp.length()-1);
                    rules.add(newRule);
                    System.out.println("unfiy("+rule1+"|"+rule2+")="+newRule);
                }
            }
        }        
    }

    public static void hornReasoning(String[] rules) {
        TreeMap trueMap = new TreeMap();
          int satisfyRuleCount;
        do {
          satisfyRuleCount = 0;
          for (int ri=0; ri<rules.length; ri++) {
              if (rules[ri].length() == 0) continue;
            String head = STR.head(rules[ri], "<-");
            String body = STR.tail(rules[ri], "<-");
            String[] conds = body.split(",");
            boolean isSatisfy = true;
            for (int ci=0; ci<conds.length; ci++) {
                if (conds[ci].length() == 0) continue;
                if (trueMap.get(conds[ci]) == null)
                    isSatisfy = false;
            }
            if (isSatisfy) {
                System.out.println(rules[ri]);
                trueMap.put(head, "1");
                rules[ri] = "";
                satisfyRuleCount ++;
            }
          }
        } while (satisfyRuleCount > 0);
    }
}

/* a-b(X),c(Y);b(X)<-d(X),e(X);c(Y)<-d(Y),f(Y);d(a);e(a);d(b);f(b) */
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page revision: 1, last edited: 11 Sep 2010 00:42
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