@InProceedings{ Kahl-1999c,
  author       = {Wolfram Kahl},
  title        = {The Term Graph Programming System {HOPS}},
  pages        = {136--149},
  booktitle    = {Tool Support for System Specification, Development and Verification},
  year = {1999},
  month = MAR,
  editor = {Rudolf Berghammer and Yassine Lakhnech},
  series = {Advances in Computing Science},
  publisher = {Springer-Verlag},
  address = {Wien},
  note        = {ISBN: 3-211-83282-3},
  abstract = {[\ldots]
    The \bf{H}igher \bf{O}bject \bf{P}rogramming \bf{S}ystem {HOPS},
    which has been developed by a group led by Gunther Schmidt
    since the mid-eighties [\ldots]
    is a graphically interactive term graph programming system
    designed for transformational program development.

    In {HOPS}, only syntactically correct and well-typed programs
    can be constructed.
    The choice of the language is only constrained by certain restrictions
    of the term graph formalism and of the typing system.

    [\ldots]
    The design of this system relies on recent advances
    in the theories of untyped and typed second-order term graphs.}
}