The Kmelia abstract component model is extended to allow the description of component compositions with multipart interactions leading to simultaneous communications between more than two services. Shared services are defined to explicitly control multipart interactions. Accordingly the communication actions of \kmelia are extended. The formal definitions of the \kmelia model, the composition of components via their services and their analysis are revisited to integrate the extension of the model. An example illustrates the need and the usage of shared services.