Algebraic theory of parameterized specifications with requirements.- A modal characterisation of observable machine-behaviour.- Trees as data and file structures.- Infinitary relations.- Full approximability of a class of problems over power sets.- How to compute generators for the intersection of subgroups in free groups.- Abstract data types and rewriting systems : Application to the programming of Algebraic Abstract Data Types in PROLOG.- Top-down tree-transducers for infinite trees I.- Easy solutions are hard to find.- Une semantique pour les arbres non deterministes.- On the algebraic specification of nondeterministic programming languages.- Applied tree enumerations.- Evaluation d'arbre pour un calcul formel (application a l'enumeration de proteines).- On pushdown tree automata.- Initial and terminal algebra semantics of parameterized abstract data type specifications with inequalities.- Calcul du rang des ?-arbres infinis regulers.- A class of tree-like UNION-FIND data structures and the nonlinearity.- Grammars without erasing rules. the OI case.- Proprietes de cloture d'une extension de transducteurs d'arbres deterministes.- Certain algorithms for subgraph isomorphism problems.- A # P-complete problem over arithmetical trees.- Trees in Kripke models and in an intuitionistic refutation system.- Efficient optimization of monotonic functions on trees.- Differents types de derivations infinies dans les grammaires algebriques d'arbres.- Discriminability of infinite sets of terms in the D?-models of the ?-calculus.