[rules-users] Unique events / facts in working memory

I'm building an application that will over time record changes in a certain component (not at any set interval, could occur any time). The component can possibly be uniquely identified via some kind of id. Is there a way that when I insert an event / fact recording a change of state in this component I can remove the previous one, so as there is only ever one fact / event recording the current state of the component. If the previous one existed it may cause rules to fire which should not. Cheers, Justin