A two argument lambda list.
A function body.
Defines a new conflict resolution tactic named
of the tactic may be
if the body does not look into the slots of the objects making up the instantiation, otherwise
binds to two instantiation objects and the function body
should return non-nil if and only if the first instantiation object is preferred to the second.
also defines a function of the same and
can be preceded by a documentation string.
(defcontext my-context :strategy (prefer-trucks))
KnowledgeWorks and Prolog User Guide (Macintosh version) - 6 Dec 2011