[drools-user] Else

[Mark Proctor]

The problem with 'else' is that it's not declarative and introduces 
large ambiguity in to your rule - which may have unwanted side effects 
over time, that you did not envision. Rules should  be precise with as 
little ambiguity as possibe - they  should describe what they do, not 
have a catch all for what they do not do. It's far better to really 
think about your rules and decide what the exact scenario you are trying 
to capture with the 'else'. In the long  run your rule's will make more 
sense for people who come back to reading them in the future and thus 
you will have a system that is easier to maintain and less susceptable 
to bugs - which is one of more compelling reasons for using a Rule Engine.

That does not mean I will not introduce 'else' in future versions of 
Drools, I still need a lot more time to evaluate it and possible 
implementations. But if it is introdoced it will still be governed by 
the above caveat.

Mark