Coordination models like Linda were first conceived in the context of closed systems — like high-performance parallel applications —, where all coordinated entities were known once and for all at design time, and coordination media were conceptually part of a coordinated application. Correspondingly, traditional formalisations of coordination models — where both coordinated entities and coordination media are uniformly represented as terms of a process algebra — endorse the viewpoint of coordination as a language for building concurrent systems.

Today, new application scenarios call for a new approach to the formalisation of coordination models and systems. The complexity of today systems requires coordination media to be seen as first-class design abstractions, affecting the engineering process down to the deployment of infrastructures providing coordination services, for which effectiveness and reliability may be critical properties demanding a formal treatment.

As a unifying framework for a number of existing works on the semantics of coordination media, in this paper we present a basic ontology and a formal framework endorsing the viewpoint of coordination as a service. Typical process algebra techniques are here exploited to represent the semantics of a coordinated system in terms of the interactive behaviour of coordination media. By this framework, coordination media are seen as primary abstractions amenable of formal investigation, promoting their exploitation at any step of the engineering process.