Implementing Modal Extensions of Defeasible Logic for the Semantic Web

Defeasible reasoning is a nonmonotonic reasoning approach in which the gaps due to incomplete information are closed through the use of defeasible rules. Defeasible logic (Nute 1994) and its variants are an important family of defeasible reasoning methods. It is a simple, efficient but flexible non-monotonic formalism that offers many reasoning capabilities embodies the concept of preference and it has low computational complexity. Recent theoretical work on defeasible logics has: (i) established some relationships to logic programming (Antoniou et al. 2006); (ii) analyzed the formal properties of these logics (Antoniou et al. 2001) and (iii) has delivered efficient implementations (Antoniou & Bikakis 2007). Its use in various application domains has been advocated, including modelling of contracts (Grosof 2004)