Theoretical Informatics and Applications April 2002 - Volume 36 - Issue 02 (Fixed Points in Computer Science (FICS'01))

The papers included in this special issue are among the more representative ones presented at the workshop Fixed Points in Computer Science (FICS’01) which took place in Florence on September 2001, as a satellite event of PLI’ 01. This was the third workshop of a series the aim of which is to provide a forum for researchers to present their results to those members of the computer science and logic communities who study or apply the fixed point operations in the different fields and formalisms. Previous workshops where held in 1998 in Brno and in 2000 in Paris (Special issues of these events also appeared in this journal). The Workshop was sponsored by Dipartimento di Sistemi ed Informatica of Universita‘di Firenze and Gruppo Nazionale per il Calcolo Scientifico of CNR. The scientific program of the workshop consisted of 5 invited lectures given by J. Adamek, Z. ́Esik, I. Guessarian, C. Stirling and R.F.C. Walters, as well as of 12 presentations chosen, after formal refereeing by the program committe members. The Program Committee was formed by: J. Adamek, R. Backhouse, S. Bloom, R. De Nicola, Z. ́Esik, I. Guessarian, W. Kuich, A. Labella, M. Mislove, D. Niwinski. The papers published here, have been selected among the presented ones after a careful refereeing by external, anonymous reviewers; I take the occasion to thank them all for the precious work. The papers of this special issue present new and significant results at least in two areas. On one hand in the algebraic theory of fixed point operators providing an equational theory that allows to find the minimal solution for a fixed point equation in a continuous idempotent semiring and the characterization in the category of sets of the class of functors that are definable by mu-terms in terms of parity games. On the other hand, we have a sophisticated example of construction of a categorical semantics for a language, but also a characterization of categories which provide a general setting for semantics in computer science with particular respect to fixed point operators