  The paper describes an extension of well-founded semantics for logic programs
with two types of negation. In this extension information about preferences
between rules can be expressed in the logical language and derived dynamically.
This is achieved by using a reserved predicate symbol and a naming technique.
Conflicts among rules are resolved whenever possible on the basis of derived
preference information. The well-founded conclusions of prioritized logic
programs can be computed in polynomial time. A legal reasoning example
illustrates the usefulness of the approach.
