Synchronization Strategies for Global Computing Models

We analyze different issues related to synchronization among multiple components in Global Computing (GC) systems, where many heterogeneous entities must cooperate in a distributed scenario with mobility. We start with a comparison between different models for GC systems, namely Fusion Calculus, Synchronized Hyperedge Replacement (SHR) with both Hoare and Milner synchronization, and logic programming. The comparison shows tight relations between the three models, while it highlights the complexity of implementing a synchronization model (Milner model) on top of another one (Hoare model). This triggers the idea of having the synchronization model as a separate entity w.r.t. the underlying framework, thus allowing to choose each time the most suitable one. This is formalized using synchronization algebras with mobility (SAMs), a generalization of Winskel's synchronization algebras apt to be used in a framework with mobility and local resources, and then applied both in the framework of SHR and of process calculi. Finally, we analyze the compositionality properties of our frameworks, with particular attention to the ``bisimilarity is a congruence' property, using standard techniques from bialgebras. As a result we show that bisimilarity is a congruence for SHR with any synchronization model, and we present a concurrent semantics for Fusion Calculus, whose induced bisimilarity is a congruence (while this does not hold for the standard semantics)