Partial clones
Abstract
A set of operations defined on a nonempty set is said to be a clone if is closed under composition of operations and contains all projection mappings. The concept of a clone belongs to the algebraic main concepts and has important applications in Computer Science. A clone can also be regarded as a many-sorted algebra where the sorts are the -ary operations defined on set for all natural numbers and the operations are the so-called superposition operations for natural numbers and the projection operations as nullary operations. Clones generalize monoids of transformations defined on set and satisfy three clone axioms. The most important axiom is the superassociative law, a generalization of the associative law. If the superposition operations are partial, i.e. not everywhere defined, instead of the many-sorted clone algebra, one obtains partial many-sorted algebras, the partial clones. Linear terms, linear tree languages or linear formulas form partial clones. In this paper, we give a survey on partial clones and their properties.
Communicated by J. Koppitz