[rules-dev] An odd couple of patterns

Has anybody ever seen a situation where a couple of patterns such as Fact( field >= 10 ) not Fact( field > 20 ) was appropriate? This does not match Facts where field isn't between 10 and 20, and so it would seem to be the same as Fact( field >= 10 && <= 20 ) but actually it doesn't match any such Fact whenever any *other* Fact with field > 20 is around. Cheers Wolfgang