Drools attempts to preserve numbers in their primitive or object wrapper form, so a variable bound to an int primitive when used in a code block or expression will no longer need manual unboxing; unlike Drools 3.0 where all primitives was autoboxed, requiring manual unboxing. A variable bound to an object wrapper will remain as an object; the existing jdk1.5 and jdk5 rules to handling auto boxing/unboxing apply in this case. When evaluating field constraints the system attempts to coerce one of the values into a comparable format; so a primitive is comparable to an object wrapper.