NKSS: a network-based knowledge system shell

This paper presents an inference network-based system for representing knowledge and performing reasoning called NKSS. In this system, all propositional concepts are represented as nodes while the relations are represented as directed links. NKSS is a four-valued system. Each proposition is either believed, its negation is believed, unknown, or in the state of contradiction. Logical relations such as AND, OR and NOT as well as other relations such as IF-THEN rules can be expressed in NKSS. There is a set of network update operators for adding, removing, updating and revising knowledge (beliefs). Due to the nature of network computation, it has an extreme level of tolerance to contradictory input knowledge. The resulting belief state is always clear and unique