Using default reasoning to discover inconsistencies in natural language requirements

The use of logic in identifying and analysing inconsistency in requirements from multiple stakeholders has been found to be effective in a number of studies. Default reasoning is a theoretically well founded formalism that is especially suited for supporting the evolution of requirements. However, direct use of logic in eliciting requirements and in discussing them with stakeholders poses serious useability problems. In this paper we explore the integration of natural language parsing techniques with default reasoning to overcome these difficulties. We also propose a method for automatically discovering scenarios that expose inconsistencies in requirements, and show how to deal with them in a formal manner. These techniques were implemented and tested in a prototype tool called CARL.