A category of explicit fusions

Name passing calculi are nowadays an established field on its own. Besides their practical relevance, they offered an intriguing challenge, since the standard operational, denotational and logical methods often proved inadequate to reason about these formalisms. A domain which has been successfully employed for languages with asymmetric communication, like the π-calculus, are presheaf categories based on (injective) relabelings, such as Set^I. Calculi with symmetric binding, in the spirit of the fusion calculus, give rise to new research problems. In this work we examine the calculus of explicit fusions, and propose to model its syntax and semantics using the presheaf category Set^E, where E is the category of equivalence relations and equivalence preserving morphisms.