CALCO the Conference on Algebra and Coalgebra in Computer Science is a high-level bi-annual
conference formed by joining CMCS (the International
WorkshoponCoalgebraicMethodsinComputerScience)andWADT(theWo-
shoponAlgebraicDevelopmentTechniques).CALCObringstogetherresearchers and practitioners to
exchange new results related to foundational aspects and both traditional and emerging uses of
algebras and coalgebras in computer s- ence. The study of algebra and coalgebra relates to the
data process and str- tural aspects of software systems. CALCO is supervised by the Steering
C- mittee co-chaired by Jos e Luiz Fiadeiro and Jan Rutten. The ?rst two CALCO conferences
took place in 2005 in Swansea Wales and in 2007 in Bergen Norway. CALCO 2009 the third
event in the series took place in Udine Italy during September 7 10 2009. CALCO 2009
received 42 submissions out of which 23 were selected for
presentationattheconference.Inspiteofarelativelylownumberofsubmissions their standard was
generally very high. The selection process was carried out by the Program Committee taking
into account the originality quality and relevance of the material presented in each
submission based on the opinions of expert reviewers four for each submission. The selected
and revised papers are included in this volume together with the contributions from the
invited speakersMaiGehrke ConorMcBride PrakashPanangadenandGordonPlotkin.
