[rules-users] DSL editor

I'm using JBoss Rules 4.0MR2. I've installed the Eclipse IDE as well and begining to work with the DSL editor. It seems to be rather easy and intuitive except for one thing. The editor provides edit fields for Expression, Mapping, Object and scope. All of which make sense except for Object. What is this used for? There doesn't seem to be any reference to this field in the documentation. Can someone please privde me with an explanation and perhaps an example? Thanks very much....