Hi, Basically, my program has 7 threads for 7 rules Rule1 Rule2 .. .. .. and they all use pattern-mattching (a rule MUST be evaluated by a thread) The problem is there are some overlapping rules, which match the same pattern and diifferent rules are likely to give different results (one rule might give a result, others might loop forever). Also, for a particular pattern, there's at least one matching rule and there may be some rule looping forever (try to evaluate a "bottom" _|_) Im thinking of getting a list of all the applicable rules for a pattern, then hopefully can choose the best rule out of it. But we have no control over the scheduling of threads, so dont know when a thread finishs its evaluation (if it is applicable rule) or it just never terminates (rule that tries evaluating a _|_) So any ideas ? TuanAnh _________________________________________________________________ Want to block unwanted pop-ups? Download the free MSN Toolbar now! http://toolbar.msn.co.uk/