This book constitutes the refereed proceedings of the 12th International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2009, held in York, UK, in March 2009, as part of ETAPS 2009, the European Joint Conferences on Theory and Practice of Software.

The 30 revised full papers presented together with two invited talks were carefully reviewed and selected from 102 full paper submissions. The topics addressed are semantics, logics and automata, algebras, automata theory, processes and models, security, probabilistic and quantitative models, synthesis, and program analysis and semantics.

This volume contains the papers presented at CONCUR 2005, the 16th - ternational Conference on Concurrency Theory. The purpose of the CONCUR series of conferences is to bring together researchers, developers, and students in order to advance the theory of concurrency and to promote its applications. This year s conference was in San Francisco, California, from August 23 to August 26. We received 100 submissions in response to a call for papers. Each subm- sionwasassignedto at leastthreemembers ofthe ProgramCommittee; in many cases, reviews were solicited from outside experts. The ProgramCommittee d- cussed the submissions electronically, judging them on their perceived imp- tance, originality, clarity, and appropriateness to the expected audience. The Program Committee selected 38 papers for presentation. Because of the format of the conference and the high number of submissions, many good papers could not be included. Although submissions werereadand evaluated, the papers that appear in this volume may di?er in form and contents from the corresponding submissions. It is expected that many of the papers will be further revised and submitted to refereed archival journals for publication."

This book constitutes the refereed proceedings of the Joint Workshop on Process Algebra and Performance Modeling and Probabilistic Methods in Verification, PAPM-PROBMIV 2001, held in Aachen, Germany in September 2001.
The 12 revised full papers presented together with one invited paper were carefully reviewed and selected from 23 submissions. Among the topics addressed are model representation, model checking, probabilistic systems analysis, refinement, Markov chains, random variables, stochastic timed systems, Max-Plus algebra, process algebra, system modeling, and the Mobius modeling framework.