David W. Etherington, Raymond Reiter
Using default logic, we formalize NETL-like inheritance hierar-chies with exceptions. This provides a number of benefits: (1) A precise semantics for such hierarchies. (2) A provably correct (with respect to the proof theory of default logic) inference algorithm for acyclic networks. (3) A guarantee that acyclic networks have extensions. (4) A provably correct quasi-parallel inference algorithm for such networks.