The Right Hand Side (RHS) is a common name for the consequence or action part of the rule; this part should contain a list of actions to be executed. It is bad practice to use imperative or conditional code in the RHS of a rule; as a rule should be atomic in nature - "when this, then do this", not "when this, maybe do this". The RHS part of a rule should also be kept small, thus keeping it declarative and readable. If you find you need imperative and/or conditional code in the RHS, then maybe you should be breaking that rule down into multiple rules. The main purpose of the RHS is to insert, retractor modify working memory data. To assist with there there are a few convenience methods you can use to modify working memory; without having to first reference a working memory instance.

"update(object, handle);" will tell the engine that an object has changed (one that has been bound to something on the LHS) and rules may need to be reconsidered.

"update(object);" can also be used, here the KnowledgeHelper will lookup the facthandle for you, via an identity check, for the passed object.

"insert(new Something());" will place a new object of your creation in working memory.

"insertLogical(new Something());" is similar to insert, but the object will be automatically retracted when there are no more facts to support the truth of the currently firing rule.

"retract(handle);" removes an object from working memory.

These convenience methods are basically macros that provide short cuts to the KnowldgeHelper instance (refer to the KnowledgeHelper interface for more advanced operations). The KnowledgeHelper interface is made available to the RHS code block as a variable called "drools". If you provide "Property Change Listeners" to your java beans that you are inserting into the engine, you can avoid the need to call "update" when the object changes.