@MASTERSTHESIS{skalka-ms-thesis,
  AUTHOR = {Christian Skalka},
  TITLE = {Some Decision Problems for {ML} Refinement Types},
  SCHOOL = {Carnegie Mellon University},
  YEAR = 1997,
  PS = {http://www.cs.uvm.edu/~skalka/skalka-pubs/skalka-ms-thesis.ps},
  ABSTRACT = {The ML \texttt{datasort} declaration is an extension to
              Standard ML allowing the declaration of \emph{refinement}
              types, which correspond to subsets of pre-existing ML
              datatypes.  Refinement types provide the programmer with
              a more precise method of expressing data structure, can
              prevent the occurence of certain run -time exceptions,
              and assist in the expression and maintenance of some
              representation invariants.  ML refinement types
              correspond to regular term and regular tree
              languages, except that refinement types are polymorphic.  While
              algorithms have been defined which determine the
              emptiness, intersection and subset problems for regular
              terms, the corresponding problems for polymorphic
              regular terms have not been studied.  This thesis
              formally describes a refinement type language, and
              defines algorithms relevant to these decision problems,
              which are proven correct.  Along with theoretical
              interest, these algorithms have practical applications
              for refinement type checking.}
}