Despite the irresistible growth of interest in formal methods and related validation and verification tools, the development of distributed systems seldom relies on them. We claim this is mainly due to formal methods lack of support for modern software life-cycles. The construction and maintenance of open distributed systems are mostly based on object-oriented software development. We investigate how frameworks may help to embed formal validation techniques in an object-oriented process based on the UMt~ notation. We show how standard model-checking techniques can be used right now on UMLmodels by exploiting informations available in class and deployment diagrams, and using an operational semantics of statecharts. We also present how the behavioural views of UML, including sequence or collaboration diagrams could be consistently managed using a common semantics model called BOL (standing for "behaviourat description language") with which the various behavioural views of UML can be translated into one another. BDL is a reactive synchronous language with a true concurrency semantics. Basic object interactions are represented in BDL by partially ordered sets of events and the behaviour of a complete (or incomplete) system is expressed by composition of basic interactions. BDL offers new perspectives for a flexible verification of systems by modeling them as globally asynchronous networks of locally synchronous software components.