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

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... sions 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. * This work has been partially supported by the DFG under grants Ha 2457/1-2 and Ha 2457/5-1.