Bounded Concurrency

. We will study systems for which a maximal number of concurrently executing (time consuming) actions is statically fixed. Two possible mechanisms of executions of actions are studied. Either the executions can be interrupted or they cannot. In the former case we show that equivalent processes remain equivalent when the number of resources (processors) which they have at disposal is changed. In the latter case, equivalences parameterized by the number of resources create a strictly decreasing hierarchy. 1 Introduction Abstract parallel programming languages (as Process Algebras) play an important role in a variety of applications. On one side they are directly used for specifications of parallel, concurrent or reactive systems of different character and complexity. On the other side they form "skeletons" of other, less abstract languages (often tailored for particular architectures). In all these cases their applicability strongly depends on how "principles" or "paradigms" of these la..