Tina, No problem. That is one of the items I think it is missing in the docs. It just means that field will be considered on the generated equals() and hashcode() methods of the bean. Example: declare Person firstName : String @key lastName : String @key address : Address end The above example will generate a Person bean class and will consider first and last name as identifiers for the person. So, two instance with the same first and last name will generate the same hashcode and the equals method will return true when comparing them, even if the address is different. Edson 2010/8/9 Tina Vießmann <tviessmann(a)stud.hs-bremen.de&gt; -- Edson Tirelli JBoss Drools Core Development JBoss by Red Hat @ www.jboss.com