Software systems are becoming inexorably more open, distributed, pervasive, mobile and connected. This thesis addresses the problem of how to build adaptive software systems. These systems need to reliably achieve system-level goals in volatile environments, where the system itself may be built from components of uncertain behaviour, and where the requirements for the software system may be changing. This thesis adopts the systemtheoretic concept of ontogenic adaptation from biology, and applies it to software architecture. Ontogenic adaptation is the ability of an individual system to maintain its organisational integrity by reconfiguring and regulating itself. A number of approaches to adaptive software architecture have been recently proposed that, to varying degrees, enable limited adaptive behaviour and reconfiguration, but none possess all the properties needed for ontogenic adaptation. We introduce a meta-model and framework called Role Oriented Adaptive Design (ROAD) that is consistent with the concept of maintaining organisational integrity through ontogenic adaptation. The ROAD meta-model defines software applications as networks of functional roles which are executed by players (objects, components, services, agents, people, or rolecomposites). These flexible organisational structures are adaptive because the relationships (contracts) between roles, and the bindings between roles and players, can be regulated and reconfigured at run-time. Such flexible organisational role-structures are encapsulated into composites each with its own organiser. Because self-managed composites are themselves role-players, these composites can be distributed and recursively composed. The organisers of the composites form a management system over which requirements and performance data pass. Rather than being monolithic constructions, ROAD software applications are dynamic, self-managed compositions of loosely-coupled, and potentially, distributed entities. The concepts in the ROAD meta-model have been implemented in a programming framework which can be extended by the application programmer to create adaptive applications. Central to this framework are dynamic contracts. These contracts define the role structure, control interactions between the role instances, and measure the performance of those interactions. Adaptivity is achieved by monitoring and manipulating these contracts, along with the role-player bindings. Contracts have been implemented using the mechanism of �association aspects�. The applicability of the ROAD framework to the domain of Service-Oriented Computing is demonstrated. The framework is further evaluated in terms of its ability to express the concept of ontogenic adaptation and also in terms of the overhead its runtime infrastructure imposes on interactions.