A method is disclosed of forward-chaining inferencing in a rulebased system having a rulebase and a set of input facts, wherein new facts are inferred in accordance with variations to the rules or the input facts, the method including: developing a computerized database containing a fact dependency tree for indicating which facts are used to produce other facts in accordance with respective rules in the rulebase; sequentially ordering the facts in the fact dependency tree to produce a serialized fact dependency tree wherein for any given fact in the sequence, all facts which are used to produce that fact are facts which are earlier in the sequence than is the given fact, and ordering the rules in the rulebase in accordance with the facts produced thereby to produce a serialized rulebase wherein the rules are in the same sequential order as the facts in the serialized fact dependency tree.