Abstract
The lack of a component concept for the UML is widely ac- knowledged. 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 pre- and postcon- dition 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 flexible contract concept shall be based on a renement relation for operations and classes, derived from operation abstractions. Abstract behaviour, expressed by pre- and post-conditions, and renement are the key elements in the denition of a formal and flexible component and component interconnection approach.