In this paper a we give a semantics for SCCS using the constructions of the topos of labelled trees. The semantics accounts for all aspects of the original formulation of SCCS, including unbounded non-determinism. Then, a partial solution to the problem of characterizing bisimulation in terms of a class of morphisms is proposed. We deene a class of… (More)
We show, for a monad T, that coalgebra structures on a T-algebra can be described in terms of " braidings " , provided that the monad is equipped with an invertible distributive law satisfying the Yang-Baxter equation.
The theoretical study of the relational model of data is ongoing and highly developed. Yet the vast majority of real databases include incomplete data, and the incomplete data is widely modelled using special values called nulls. As noted many times by Date and others, the inclusion of special values is not compatible with the relational model and… (More)
A model of computation on multi-dimensional words, based on the overlapping operation , induces a categorical structure, to which a new type of logic corresponds, whose formulae express properties of computations in a language containing all first order formulae. While the resulting deductive system is strictly less powerful than (intuitionistic) first… (More)