D-fusion: A distinctive fusion calculus

Abstract. We study the relative expressive power of Fusion and pi-calculus. Fu-sion is commonly regarded as a generalisation of pi-calculus. Actually, we prove that there is no uniform fully abstract embedding of pi-calculus into Fusion. This fact motivates the introduction of a new calculus, D-Fusion, with two binders, λ and ν. We show that D-Fusion is strictly more expressive than both pi-calculus and Fusion. The expressiveness gap is further clarified by the existence of a fully abstract encoding of mixed guarded choice into the choice-free fragment of D-Fusion.