@INPROCEEDINGS{Hanus90ALP,
author = "Hanus, M.",
title = "Logic Programs with Equational Type Specifications",
booktitle = "Proc.\ of the 2nd International Conference on Algebraic and
Logic Programming",
publisher="Springer LNCS 463",
pages = "70-85",
year = 1990,
note = "Extended version in {\em Types in Logic Programming}, MIT Press, 1992",
abstract = {
This paper proposes a framework for logic programming with
different type systems. In this framework a typed logic program
consists of a type specification and a Horn clause program
which is well-typed with respect to the type specification.
The type specification defines all types which can be used
in the logic program. Relations between types are expressed
by equations on the level of types. This permits the specification
of many-sorted, order-sorted, polymorphic and
polymorphically order-sorted type systems.
We present the declarative semantics of our framework
and a resolution procedure
for typed logic programs. Resolution requires a
unification procedure for typed terms which is based on a
unification procedure for the type theory. An interesting application
is a type system that combines parametric polymorphism
with order-sorted typing and permits higher-order logic programming.
Moreover, our framework sheds some
new light on the role of types in logic programming.
}, }