  This volume contains the proceedings of the Combined 19th International
Workshop on Expressiveness in Concurrency and the 9th Workshop on Structural
Operational Semantics (EXPRESS/SOS 2012), which took place on 3rd September
2012 in Newcastle upon Tyne, as a satellite workshop of CONCUR 2012. The
EXPRESS workshop series aims at bringing together researchers interested in the
expressiveness of various formal systems and semantic notions, particularly in
the field of concurrency. The SOS workshop series aims 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. In 2012, the EXPRESS and SOS communities organized a joint
EXPRESS/SOS 2012 workshop on the formal semantics of systems and programming
concepts, and on the expressiveness of mathematical models of computation.
