Strategies as Concurrent Processes

Concurrent strategies are shown to support operations yielding an economic yet rich higher-order concurrent process language, which shares features both with process calculi and nondeterministic dataflow. Its operational semantics and ‘may and must’ equivalence require that we take internal (neutral) moves seriously, leading to the introduction of ‘partial strategies’ which may contain neutral moves. Through partial strategies, we can present a transition semantics for a language of strategies and can formulate their ‘may and must’ behaviour. While partial strategies compose, in a way extending that of strategies, in general composition introduces extra neutral moves; in particular, copy-cat is no longer strictly an identity w.r.t. composition. However, a simple extension of concurrent strategies (with stopping configurations) maintains the fact that they form a bicategory while still capturing ‘may and must’ behaviour.