This collection of current research on logic programming languages presents results from a three-year, ESPRIT-funded effort to explore the integration of the foundational issues of functional, logic, and object-oriented programming. It offers valuable insights into the fast-developing extensions of logic programming with functions, constraints, concurrency, and objects. Chapters are grouped according to the unifying themes of functional programming, constraint, logic programming, and object-oriented programming. K. R. Apt and J. W. de Bakker are Professors and J.J. M. M. Rutten is Research Scientist, all at the Centrum voor Wiskinde en Informatica in Amsterdam.