A confluent relational calculus for higher-order programming with constraints

Abstract

We present the ρ-calculus, a relational calculus parametrized with a logical constraint system. The ρ-calculus provides for higher-order relational programming with first-order constraints, and subsumes higher-order functional programming as a special case. It captures important aspects of the concurrent constraint programming language Oz. We prove the uniform confluence of the ρ-calculus. Uniform confluence implies that all maximal derivations issuing from a given expression have equal length. But even confluence of a nonfunctional calculus modelling computation with partial information is interesting on its own right.