**19 March 2012
Amsterdam, The Netherlands**

COIN, or Coalgebra in the Netherlands, is a seminar taking place alternating at the Radboud University Nijmegen and the CWI in Amsterdam. The aim of COIN is to bring together coalgebra researchers from various locations in the Netherlands, and share current results and questions in the world of coalgebra. We welcome presentations on any subject related to coalgebra. The next COIN meeting is scheduled for Monday, 19 March 2012, at the CWI, in room L120. The schedule is as follows: 13:30 - 14:15 Georgiana Caltais (Reykjavik University Iceland) Final Semantics for Decorated Traces 14:15 - 15:00 Tomasz Brengos (Warsaw University of Technology) Weak bisimulations for coalgebras over ordered functors 15:15 - 16:00 Clemens Kupke (University of Oxford) Dualities and minimal automata COIN is coordinated by Marcello Bonsangue (Leiden University/CWI), Bart Jacobs (Radboud Universiteit Nijmegen), and Jan Rutten (CWI/Radboud Universiteit Nijmegen), and its website can be found at http://homepages.cwi.nl/~winter/coin.html Abstracts ========= Georgiana Caltais (Reykjavik University Iceland) Final Semantics for Decorated Traces ------------------------------------ In concurrency theory, various semantic equivalences on labelled transition systems are based on traces enriched or decorated with some additional observations. They are generally referred to as decorated traces, and examples include ready, failure, trace and complete trace equivalence. In this talk we shall apply the generalized powerset construction in order to give a coalgebraic presentation of decorated trace semantics. This will allow us to provide a uniform notion of canonical, minimal representatives for the various decorated trace equivalences, in terms of final Moore automata. As a consequence, we shall see how proofs of decorated trace equivalence can be given by coinduction, using different types of (Moore-) bisimulation, which is helpful for automation. This is joint work with Filippo Bonchi (LIP-ENS Lyon), Marcello Bonsangue (Leiden University/CWI), Jan Rutten (CWI/Radboud University Nijmegen), and Alexandra Silva (Radboud University Nijmegen, CWI). Tomasz Brengos (Warsaw University of Technology) Weak bisimulations for coalgebras over ordered functors ------------------------------------------------------- The aim of this talk is to introduce a coalgebraic setting in which it is possible to generalize and compare the two known approaches to weak bisimulation for labelled transition systems. To be more precise, for an ordered functor F and a class of F-coalgebras satisfying some additional properties we define a coalgebraic saturator which will serve as the base for two approaches to generalizing weak bisimulation. Although the two ways of defining weak bisimulation for LTS are known to be equivalent, we will show that in the general setting of ordered functors they do not always have to coincide. We will give sufficient conditions for them to match and present interesting examples of functors and coalgebras where they differ. Finally, we will talk about restrictions of the generalization and problems for further research. Clemens Kupke (CWI) Dualities and minimal automata ------------------------------ In my talk I am going to describe how dualities between categories of finite automata (coalgebras) and algebras can be used in order to obtain Brzozowski-like minimisation constructions for different types of (deterministic) automata. In particular, I will focus on linear weighted and probabilistic automata. This is joint work with Nick Bezhanishvili and Prakash Panangaden.