An Emptiness Algorithm for Regular Types with Set Operators
  An algorithm to decide the emptiness of a regular type expression with set operators given a set of parameterised type definitions is presented. The algorithm can also be used to decide the equivalence of two regular type expressions and the inclusion of one regular type expression in another. The algorithm strictly generalises previous work in that tuple distributivity is not assumed and set operators are permitted in type expressions. 
Lunjin Lu and John G. Cleary (University of Waikato)