Components, Contracts, and Connectors for the Unified Modelling Language UML

The lack of a component concept for the UML is widely acknowledged. Contracts between components can be the starting point for introducing components and component interconnections. Contracts between service providers and service users are formulated based on abstractions of action and operation behaviour using the preand postcondition technique. A valid contract allows to establish an interconnection a connector between the provider and the user. The contract concept supports the re-use of components by providing means to establish and modify component interconnections. A exible contract concept shall be based on a re nement relation for operations and classes, derived from operation abstractions. Abstract behaviour, expressed by preand postconditions, and re nement are the key elements in the de nition of a formal and exible component and component interconnection approach.