/ Published in: Java
Artificial intelligence basics : This is a forward chaining implementation which works with horn form knowledge bases. Had some trouble finding any simple and easy to understand examples online - so here's my version!!!
http://en.wikipedia.org/wiki/Forward_chaining
http://en.wikipedia.org/wiki/Forward_chaining
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import java.util.*; import java.io.*; // to run simply do a: new FC(ask,tell) and then fc.execute() // ask is a propositional symbol // and tell is a knowledge base // ask : r // tell : p=>q;q=>r;p;q; class FC{ // create variables public static ArrayList<String> agenda; public static ArrayList<String> facts; public static ArrayList<String> clauses; public static ArrayList<Integer> count; public static ArrayList<String> entailed; // initialize variables agenda = new ArrayList<String>(); clauses = new ArrayList<String>(); entailed = new ArrayList<String>(); facts = new ArrayList<String>(); count = new ArrayList<Integer>(); tell = t; ask = a; init(tell); } // method which calls the main fcentails() method and returns output back to iengine if (fcentails()){ // the method returned true so it entails output = "YES: "; // for each entailed symbol for (int i=0;i<entailed.size();i++){ output += entailed.get(i)+", "; } output += ask; } else{ output = "NO"; } return output; } // FC algorithm public boolean fcentails(){ // loop through while there are unprocessed facts while(!agenda.isEmpty()){ // take the first item and process it // add to entailed entailed.add(p); // for each of the clauses.... for (int i=0;i<clauses.size();i++){ // .... that contain p in its premise if (premiseContains(clauses.get(i),p)){ // reduce count : unknown elements in each premise count.set(i,--j); // all the elements in the premise are now known if (count.get(i)==0){ // the conclusion has been proven so put into agenda // have we just proven the 'ask'? if (head.equals(ask)) return true; agenda.add(head); } } } } // if we arrive here then ask cannot be entailed return false; } // method which sets up initial values for forward chaining // takes in string representing KB and seperates symbols and clauses, calculates count etc.. for (int i=0;i<sentences.length;i++){ if (!sentences[i].contains("=>")) // add facts to be processed agenda.add(sentences[i]); else{ // add sentences clauses.add(sentences[i]); count.add(sentences[i].split("&").length); } } } // method which checks if p appears in the premise of a given clause // input : clause, p // output : true if p is in the premise of clause // check if p is in the premise if (conjuncts.length==1) return premise.equals(p); else } }
URL: http://en.wikipedia.org/wiki/Forward_chaining