In two earlier papers we derived congruence formats for weak semantics on the basis of a decomposition method for modal formulas. The idea is that a congruence format for a semantics must ensure that the formulas in the modal characterisation of this semantics are always decomposed into formulas that are again in this modal characterisation. Here this work is extended with important stability a...

The coupled simulation equivalence is slightly larger than observation equivalence. Where observation equivalence is based on weak bisimulations, coupled simulation equivalence is based on pairs of simulations which coincide at stable states. We establish the corresponding congruence and provide a complete axiomatization by adding a new-law, :(:P + Q) = :P + Q, to the axioma-tization of observa...

On the basis of the concept of interval valued intuitionistic fuzzy set introduced by K. Atanassov [3], the notion of interval valued intuitionistic fuzzy subsemigroup (ideal, bi-ideal, (1, 2)-ideal) of a semigroup with respect to t-norm T and s-norm S is given and the characteristic properties are described. The homomorphic image and inverse image are investigated. In particular, by the help o...

in this note first we define the notions of fuzzy positive implicativehyper bck-ideals of types 1,2,3 and 4. then we prove some theorems whichcharacterize the above notions according to the level subsets. also we obtainthe relationships among these notions, fuzzy (strong, weak, reflexive) hyperbck-ideals and fuzzy positive implicative hyper bck-ideals of types 5,6,7and 8. then, we define the no...

The paper deals with weak congruences of algebras having at least two constants in the similarity type. The presence of constants is a necessary condition for complementedness of the weak congruence lattices of non-trivial algebras. Some sufficient conditions for the same property are also given. In particular, so called 0,1-algebras have complemented weak congruence lattices if and only if the...

Prefix iteration is a variation on the original binary version of the Kleene star operation P Q, obtained by restricting the first argument to be an atomic action. The interaction of prefix iteration with silent steps is studied in the setting of Milner’s basic CCS. Complete equational axiomatizations are given for four notions of behavioural congruence over basic CCS with prefix iteration, viz...

In this paper, an O-convergence theory of fuzzy nets is built in L-topological spaces by means of neighborhoods of fuzzy points. It has many nice properties. It can be used to characterize the closed set, open set, T2 separation axiom and fuzzy compactness. c © 2003 Elsevier B.V. All rights reserved.