Meta-level selection techniques for the control of default reasoning

The problem how to control default reasoning is addressed. In an earlier work it was described how selection functions (on default conclusions) added to default logic can be exploited to describe control. In this paper specific properties of selection functions are described. Moreover, we investigate under which conditions selection functions can be expressed in the form of declarative control knowledge at the meta-level. Furthermore, we show that normal default logic with additional control by selection functions is (in some sense) equivalent to default logic in general. Finally, an alternative approach to control is introduced based on inhibition relations between default rules.