exp(ASPc) : Explaining ASP Programs with Choice Atoms and Constraint
  Rules
  We present an enhancement of exp(ASP), a system that generates explanation
graphs for a literal l - an atom a or its default negation ~a - given an answer
set A of a normal logic program P, which explain why l is true (or false) given
A and P. The new system, exp(ASPc), differs from exp(ASP) in that it supports
choice rules and utilizes constraint rules to provide explanation graphs that
include information about choices and constraints.
