This paper proposes a calculus for describing communication-centred programs and discusses its use through a formal description of several use cases from real business protocols. The formalism, called global calculus, aims at representing global message flows as structured communications. The global calculus originates from the Choreography Description Language (CDL), a web service description language developed by W3C’s WS-CDL Working Group. Its type discipline is based on session types which have been studied g years in the context of the π-calculus [15,10,22,6]. Session types offer a high-level abstraction and articulation for complex communication behaviours, and play a fundamental role to guide the programmer towards a clear, well-structured description of business protocols.