Composite systems are generally comprised of heterogeneous components whose specifications are developed by many development participants. The requirements of such systems are invariably elicited from multiple perspectives which overlap, complement and contradict each other. Furthermore, these requirements are generally developed and specified using multiple methods and notations respectively. It is therefore necessary to express and check the relationships between the resultant specification fragments. In this paper we deploy multiple "ViewPoints" that hold partial requirements specifications, described and developed using different representation schemes and development strategies. We discuss the notion of interViewPoint communication in the context of this ViewPoints framework, and propose a general model for ViewPoint interaction and integration. We elaborate on some of the requirements for expressing and enacting inter-ViewPoint relationships - the vehicles for consistency che...

Adaptability, i.e. the ability of a system to adapt dynamically to changes in its execution environment, is considered as an important property of computer systems. Scaling directory replication in name servers and load balancing are well known examples. However, adaptability in today's systems, if present at all, generally is burnt in and dedicated to singular properties of the execution environment. This paper discusses a more universal approach to adaptability. The approach is based on the --- in some cases artificial --- separation of nonfunctional properties from the functionality of application systems. The scheme provides full control over non functional properties while preserving transparency for the application programs. To study that approach, reflection has been incorporated into the BirliX object model and its implementation. It has been used to experiment with some non functional properties such as migration and protection. The paper motivates the need for a universal ada...