Automatic Belief Revision in SNePS
  SNePS is a logic- and network- based knowledge representation, reasoning, and acting system, based on a monotonic, paraconsistent, first-order term logic, with compositional intensional semantics. It has an ATMS-style facility for belief contraction, and an acting component, including a well-defined syntax and semantics for primitive and composite acts, as well as for ``rules'' that allow for acting in support of reasoning and reasoning in support of acting. SNePS has been designed to support natural language competent cognitive agents.   When the current version of SNePS detects an explicit contradiction, it interacts with the user, providing information that helps the user decide what to remove from the knowledge base in order to remove the contradiction. The forthcoming SNePS 2.6 will also do automatic belief contraction if the information in the knowledge base warrents it. 
Stuart C. Shapiro and Frances L. Johnson