We extend the ASPIC+ framework for structured argumentation so as to allow
applications of the reasoning by cases inference scheme for defeasible
arguments. Given an argument with conclusion `A or B', an argument based on
A with conclusion C, and an argument based on B with conclusion C, we
allow the construction of an argument with conclusion C. We show how our
framework leads to different results than other approaches in non-monotonic
logic for dealing with disjunctive information, such as disjunctive default
theory or approaches based on the OR-rule (which allows to derive a defeasible
rule `If (A or B) then C', given two defeasible rules `If A then C'
and `If B then C'). We raise new questions regarding the subtleties of
reasoning defeasibly with disjunctive information, and show that its
formalization is more intricate than one would presume.Comment: Proceedings of SAC/KRR 201