We propose a new programming model that supports a compositionality of choreographies. The key of our approach is the introduction of partial choreographies, which can mix global descriptions with communications among external peers. We prove that if two choreographies are composable, then the endpoints independently generated from each choreography are also composable, preserving their typability and deadlock-freedom. The usability of our framework is demonstrated by modelling an industrial use case implemented in a tool for Web Services, Jolie.