The existence and the construction of a specification morphism between two algebraic specifications is a crucial step in modular system design and in the reusability of software. The problem of determining the existence of a signature morphism between two algebraic signatures is analyzed and proved to be NP-complete by reducing the well known 3SAT problem. As a consequence, the problem of findi...

INTRODUCTION Huxley, Mayr, Osmond, and Hoffer (1964) presented a hypothesis that schizophrenia is a genetic morphism (see Huxley, 1955). This is in general agreement with the proposition that all genetic characteristics which exist in a population at a frequency higher than can be maintained by mutation alone must be a morphism. The frequency of the morphic gene is the result of a balance betwe...

A nonerasing morphism σ is said to be weakly unambiguous with respect to a word s if σ is the only nonerasing morphism that can map s to σ(s), i. e., there does not exist any other nonerasing morphism τ satisfying τ(s) = σ(s). In the present paper, we wish to characterise those words with respect to which there exists such a morphism. This question is nontrivial if we consider so-called length-...

Polar spaces are presented from the point of view of paraprojective spaces. Morphisms are introduced and some immediate categorical aspects are reviewed. The morphisms of polar spaces are then studied in more details and are shown to preserve the spaces’ structure. Finally, it is shown that a morphism of polar spaces can be split into a morphism of nondegenerate polar spaces and a morphism of p...

In order to study relative PCF-definability of boolean functions, we associate a hypergraph Hf to any boolean function f (following [2, 4]). We introduce the notion of timed hypergraph morphism and show that it is: – Sound: if there exists a timed morphism from Hf to Hg then f is PCF-definable relatively to g. – Complete for subsequential functions: if f is PCF-definable relatively to g, and g ...

Using the fact that the Parikh matrix mapping is not an injective mapping, the paper investigates some properties of the set of words having the same Parikh matrix; these words are called “amiable” or “M equivalent”. The presented paper uses the results obtained in [3] for the binary case. The aim is to distinguish the amiable words by using a morphism that provides additional information about...

Every morphism from ℙ n to