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We prove the following completeness theorem: If the fixed point operation over a category is defined by initial@, then the equations satisfied by the fixed point operation are exactly those of iteration theories. Thus, in such categories, the equational axioms of iteration theories provide a sound and complete axiomatization of the equational properties of(More)
1 Abstract. In this paper we propose a new formal operation on words and languages, called superposition. By this operation, based on a Watson-Crick-like complementarity, we can generate a set of words, starting from a pair of words, in which the contribution of a word to the result need not be one subword only, as happens in classical bio-operations of DNA(More)
The use of the Web and the diffusion of knowledge management systems makes it possible to base discussions upon a vast set of documents, many of which also include links to multimedia material, such as images or videos. This perspective could be exploited by allowing a team to collaborate by exchanging and retrieving annotated multimedia documents (text,(More)
A membrane system (P system) is a model of computation inspired by some basic features of the structure and behaviour of living cells. In this paper we consider systems with string-objects processed by rewriting, with the communication controlled by conditions on the contents of the strings. Symbols, substrings (in an arbitrary place, or as a(More)
Nondeterminism is a direct outcome of interactions and is, therefore a central ingredient for modelling concurrent systems. Trees are very useful for modelling nondeterministic behaviour. We aim at a tree-based interpretation of regular expressions and study the effect of removing the idempotence law X+X=X and the distribution law X v (Y+Z)=X vY+X vZ from(More)
An important field for model-driven development of interfaces is the consideration of users with disabilities. Interface design for deaf people presents specific problems, since it needs to be based on visual communication, incorporating unusual forms of interaction, in particular gesture-based ones. Standard solutions for model-driven development of visual(More)
CoPuppet is a framework for the development of performances of virtual puppetry. In particular, it defines a class of interactive systems in which to realize collaborative performances involving several puppeteers. Users are able to control puppets' body parts and interact with the puppets by producing gestures which are captured by video devices and(More)
The logical characterization of the strong and the weak (ignoring silent actions) versions of resource bisimulation are studied. The temporal logics we introduce are variants of Hennessy-Milner Logics that use graded modalities instead of the classical box and diamond operators. The considered strong bisimulation induces an equivalence that, when applied to(More)
We provide a finite equational axiomatization for bisimulation equivalence of nondeterministic interpretation of regular expressions. Our axiomatization is heavily based on the one by Salomaa, that provided an implicative axiomatization for a large subset of regular expressions, namely all those that satisfy the non-empty word property (i.e. without 1(More)