Processes as data types: Observational semantics and logic -- Metric pomset semantics for a concurrent language with recursion -- Fault-tolerant naming and mutual exclusion -- Flow event structures and flow nets -- Three equivalent semantics for CCS -- Towards a semantic approach to SIMD architectures and their languages -- Concerning the size of clocks -- Transition systems with algebraic structure as models of computations -- Concurrency and computability -- Causal trees interleaving + causality -- Partially commutative formal power series -- Infinite traces -- Equivalences and refinement -- CCS and petri nets -- About fixpoints for concurrency -- Observers, experiments, and agents: A comprehensive approach to parallelism -- Action versus state based logics for transition systems -- Approaching fair computations by ultra metrics -- On distributed languages and models for distributed computation.

This volume contains the proceedings of the 1990 Spring School of Theoretical Computer Science, devoted to the semantics of concurrency. The papers are of two kinds: - surveys and tutorials introducing the subject to novices and students and giving updates of the state of the art, - research papers presenting recent achievements in the semantics of concurrency. The contributions explicate the connections, similarities and differences between various approaches to the semantics of concurrency, such as pomsets and metric semantics, event structures, synchronization trees, fixpoints and languages, traces, CCS and Petri nets, and categorical models. They also cover and compare the various notions of observation and bisimulation equivalences, logics for concurrency, and applications to dis- tributed systems.