ALE defeasible description logic

One of Semantic Web strengths is the ability to address incomplete knowledge. However, at present, it cannot handle incomplete knowledge directly. Also, it cannot handle non-monotonic reasoning. In this paper, we extend ALC- Defeasible Description Logic with existential quantifier, i.e., ALE Defeasible Description Logic. Also, we modify some parts of the logic, resulting in an increasing efficiency in its reasoning.