1. A method of facilitating an exchange of messages between a remote client application and a server system, the server system being capable of supporting a plurality of application program interfaces (APIs) that includes a targeted API, the method including: receiving a plurality of request messages generated by the remote client application, each request message requesting an activity to be performed by the targeted API, with respect to an associated application, and comprising: at least one data component, and a request component including a reusable identified schema definition specific to the targeted API.