Defeasible Reasoning with Prototype Descriptions: A New Preference Order

The representation of defeasible information in Description Logics is a well-known issue and many formal
approaches have been proposed. However, in these proposals, little attention has been devoted to studying
their capabilities in capturing the interpretation of typicality and exceptions from an ontological and cognitive
point of view. In this regard, we are developing a model of defeasible knowledge for description logics based
on combining ideas from prototype theory, weighted description logic (aka ‘tooth logic’), and earlier work on
justifiable exceptions. This machinery is then used to determine exceptions in case of conflicting axioms. In this
paper, we analyse this formalisation with respect to some interesting cases where the defeasible properties to
which we may have exceptions are also present as features in prototype descriptions. The analysis will suggest
that a new preference order, which considers what happens inside the models, may be best suited and we outline
how this new preference order can be defined.