  This volume contains the proceedings of the Combined 22nd International
Workshop on Expressiveness in Concurrency and the 12th Workshop on Structural
Operational Semantics (EXPRESS/SOS 2015) which was held on 31 August 2015 in
Madrid, Spain, as an affiliated workshop of CONCUR 2015, the 26th International
Conference on Concurrency Theory. The EXPRESS workshops aim at bringing
together researchers interested in the expressiveness of various formal systems
and semantic notions, particularly in the field of concurrency. Their focus has
traditionally been on the comparison between programming concepts (such as
concurrent, functional, imperative, logic and object-oriented programming) and
between mathematical models of computation (such as process algebras, Petri
nets, event structures, modal logics, and rewrite systems) on the basis of
their relative expressive power. The EXPRESS workshop series has run
successfully since 1994 and over the years this focus has become broadly
construed. The SOS workshops aim at being a forum for researchers, students and
practitioners interested in new developments, and directions for future
investigation, in the field of structural operational semantics. One of the
specific goals of the SOS workshop series is to establish synergies between the
concurrency and programming language communities working on the theory and
practice of SOS. Since 2012, the EXPRESS and SOS communities have organized an
annual combined EXPRESS/SOS workshop on the expressiveness of mathematical
models of computation and the formal semantics of systems and programming
concepts.
