Composition and decomposition of multiparty sessions

Multiparty sessions are systems of concurrent processes, which allow several participants to communicate by sending and receiving messages. Their overall behaviour can be described means global types. Typable multiparty enjoy lock-freedom. We look at as open allowing one compose transforming two their into a pair coupled gateways, forwarding messages between the sessions. Gateways need compatible. show that session resulting from composition typed, its type computed types starting As consequence, lock-freedom is preserved composition. Compatibility necessary, since obtained composing with incompatible have locks (or they not sessions). also define direct composition, allows connect without using gateways. Finally, we propose decomposition operator, split two, left inverse Direct on prepare ground for novel framework modular design implementation distributed systems.