Hi, In your case introduce a discountedPrice field, leaving the original price alone. If you insist on making it run only once instead, you can introduce a field or fact class to mark an order "discounted", then all discounting rules know to ignore it. (This gets really complicated if the order amount ever changes and you do need to run the discounting rules again.) Gabor 2011/3/18 yong zhao <cluncao(a)yahoo.com.cn&gt;:

thanks , Both are possible ways for the issue though they are a little complicated. ________________________________ 发件人： Michael Anstis <michael.anstis(a)gmail.com&gt; 收件人： Rules Users List <rules-users(a)lists.jboss.org&gt; 发送日期： 2011/3/19 (周六) 12:25:48 上午 主 题： Re: [rules-users] how to ensure that one rule only is executed once? You'd need to make sure you inform the engine that Order's price has changed:- when ... then modify( $o ) { setPrice( $o.getPrice() - 20); } You could also consider using agenda-groups or lock-on-active to provide your behaviour. agenda-groups rule "rule 1" //implied default agenda-group of MAIN when $o : Order (amount>100 && <200); then modify( $o ) { setPrice( $o.getPrice() - 10); } drools.setFocus("next step in calculation"); end rule "rule 2" //implied default agenda-group of MAIN when $o:Order (amount>200); then modify( $o ) { setPrice($o.getPrice() - 20); } drools.setFocus("next step in calculation"); end rule "rule 3" agenda-group "next step in calculation" when $o : Order(....) then .... end lock-on-active rule "rule 1" //implied default agenda-group of MAIN lock-on-active true when $o : Order (amount>100 && <200); then modify( $o ) { setPrice( $o.getPrice() - 10); } end rule "rule 2" //implied default agenda-group of MAIN lock-on-active true when $o:Order (amount>200); then modify( $o ) { setPrice($o.getPrice() - 20); } end rule "rule 3" agenda-group "next step in calculation" when $o : Order(....) then .... end On 18 March 2011 16:08, Gabor Szokoli <szocske(a)gmail.com&gt; wrote: Hi,