Telecommunication operators provide services and enable customers to compose their own packages of services. While designing a service-oriented system, deciding whether a service interaction is desired or harmful is a subjective choice which depends on the requirements expressed by the user with respect to the service integration. In this paper, we define both a formalism and a methodology which, respectively, allow us to automatically analyse interactions based on specification consistency. For the latter (i.e. the methodology), we take advantage of both specifier expertise and formal methods.Hence, adding a new service on a system consists in a static design step providing a consistent specification and thus aiming to reinforce the specification quality, taking into account the expert choices. Service requirements are expressed by means of an axiomatic formalism which includes variables, invariant properties and state transition rules, also called pre-post formulas. The interaction analysis is based on algorithms which check specification consistency. Each detected interaction is then avoided thanks to an expert choice correcting the anomaly.