[rules-users] Filter incorrect abbreviations

Hello Droolers, I'm a Drools novice and I'm stuck with a basic rule problem. In my domain I use a list of abbreviations to describe the conditions of a system. Before I can check the state of my system I have to verify all applied abbreviations. The List of abbreviations is not a fixed list it's more like a combination of chars, combined in different ways on fixed positions. This is a small cutout: A cutout of possible chars at Position 1: A B C D F H A cutout of possible chars at Position 2: - A C s n b A cutout of possible chars at Position 3: - A B E F M A cutout of possible chars at Position 4: - H L O R U Now it is allowed to combine the following abbreviations: (another small cutout) A--O A--R A--U A--L BAAO BAAR BAAU BAAL but it is not allowed to combine this: AA** B-** (* stands for all possible chars on a position) Now I have 2 basic Questions: 1) How can I pick abbreviations that are NOT allowed? I think it's easy to say: rule "Rule 1" when a : Abbreviation( pos1 == 'A', pos2 == '-', pos3 == '-', pos4 == 'O' ) then # do something positiv end But how can I pick up all the wrong combinations without hardcoding them? This would end up in a never-ending story. 2) Upgrading the "Rule 1" from my 1st Question I'm looking for a way to make the Rules more generic. I don't want to hardcode all possible abbreviation combinations. How can I realise something like this VERY INFORMAL notation: rule "Rule 2" when a : Abbreviation( pos1 == 'A', pos2 == ['-','D','H'], pos3 == '-', pos4 == ['O', 'R', 'U', 'L'] ) # If abbreviation looks like A--O, AD-O, AD-U, AH-R, etc. everything is fine. # It's time for "Rule 2" to do something positiv then # do something positiv end "Rule 2" should find all the abbreviations that are build up according to a set of allowed char combinations. OR rule "Rule 3" when a : Abbreviation( pos1 == 'A', pos2 != ['-','D','H'], pos3 != '-', pos4 != ['O', 'R', 'U', 'L'] ) # If abbreviation looks like AA-O, AB-U, A-AO, A--K, etc. something is wrong. # It's time for "RULE 3" to announce something negative then # announce something negative end "Rule 3" should filter all the abbreviations that are violating a set of allowed char combinations. Thanx 2 all droolers in advance. Pete