A. P. Courtney, N. Y. Foo, G. Antoniou
Default logic is a useful formalism for reasoning with incomplete information, its intuitive characteristics making it particularly suited for applications. Exten is a system currently capable of computing first-order Reiter, Justified and Constrained default extensions. It is part of a project to create a full default logic workbench, with future work involving query evaluation, further support for default variants and integration with belief revision. As such, it has been implemented in an object-oriented manner, and is designed to facilitate experimentation. The interface is based around a small language, giving the user flexibility in editing default theories and changing various parameters (such as compute next n extensions or carry out success checks every m steps).