@INPROCEEDINGS{BrasselHanusHuch04JFLP,
author       = {Bra{\ss}el, B. and Hanus, M. and Huch, F.},
title        = {Encapsulating Non-Determinism in Functional Logic Computations},
year         = {2004},
signature    = {nocopy},
keywords     = {functional programming, logic programming, semantics},
journal      = {Journal of Functional and Logic Programming},
number       = {6},
publisher    = {EAPLS},
volume       = {2004},
abstract = {
One of the key features of the integration of functional and logic
languages is the access to non-deterministic computations from the
functional part of the program.  In order to ensure the determinism
of top-level computations in a functional logic program, which is
usually a monadic sequence of I/O operations, one has to encapsulate
the non-determinism (i.e., search for solutions) occurring in logic
computations.  However, an appropriate approach to encapsulation can
be quite subtle if subexpressions are shared, as in lazy evaluation
strategies.  In this paper we examine the current approaches to
encapsulate non-deterministic computations for the declarative
multi-paradigm language Curry, show their relative advantages and
the problems they induce. Furthermore, we present a new approach which
combines the advantages but avoids the problems.  Our proposal is
based on providing a primitive I/O action for encapsulation from
which various specialized search operators can be derived.  In order
to provide a formal foundation for this new approach to
encapsulation, we define the operational semantics of this new
primitive.
}
}