Global network connectivity has enabled accessibility to a wide range of geographically dispersed services. By encapsulating and representing such services as components, they can be effectively composed into sophisticated wide-area applications that otherwise would be much harder to build. This paper presents a component model for encapsulating such services and a composition model for assembling encapsulated and possibly active services into new applications, while preserving the administrative autonomy of sites and individual components. The component model is dynamically and self-adaptable, allowing for the adjustment of structure and behavior of autonomous components to changing or previously unknown contexts in which they need to operate. The composition model includes a set of protocols that enable us to dynamically deploy live components into remote sites and to dynamically reconfigure the deployment scheme through reflective stubs termed Ambassadors. The component and composition models have been fully implemented in Hadas, which also includes a host of tools for the creation, deployment, and composition of autonomous components.

No abstract available.

The explosive growth in global networking infrastructures has created the opportunity to construct systems involving large number of independent and widely-distributed computational components. Administrative and operational autonomy considerations imply that the actual establishment of agreements regarding all aspects of component interaction must be explicitly declared and effectively formed. Moreover, since agreements may evolve over time, their representation needs to be highly tailorable. Design autonomy considerations imply the need to interoperate between pre-existing components, yet not enforce a fixed interoperability standard. The HADAS system addresses both concerns by providing a model and a corresponding programmable interface to component interoperability. Specifically, it provides an integration framework in which components "live", a peer-based configuration model for forming agreements and interconnections between components, and a coordination language for explicitly programming the actual desired distributed computation using these components. The framework rests on an underlying reflective object model that supports mutability and mobility, and an infrastructure that provides object interconnectivity, security and persistence. HADAS is fully implemented in Java and comes with a full programming environment for developing and executing network-centric applications.

Mobile software objects are computational entities that travel in large-scale and widely-distributed heterogeneous systems, and whose functionality can be attached to diverse computing environments. When employed over decentralized sites with operational and administrative autonomy, support for mobility raises difficult issues with respect to object management services. In particular it impacts persistence, reference handling, object naming, and requires extensive support for security. This paper discusses the requirements from an object management system that incorporates mobile, autonomous and reflective objects and presents the design and implementation of the Mobile Object Manager (MOM) which fulfills these requirements.

The explosive growth in global networking infrastructures has created the opportunity to construct systems involving large number of independent and widely-distributed computational components. Administrative and operational autonomy considerations imply that the actual establishment of agreements regarding all aspects of component interaction must be explicitly declared and effectively formed. Moreover, since agreements may evolve over time, their representation needs to be highly tailorable. Design autonomy considerations imply the need to interoperate between pre-existing components, yet not enforce a fixed interoperability standard. The HADAS system addresses both concerns by providing a model and a corresponding programmable interface to component interoperability. Specifically, it provides an integration framework in which components "live", a peer-based configuration model for forming agreements and interconnections between components, and a coordination language for explicitly programming the actual desired distributed computation using these components. The framework rests on an underlying reflective object model that supports mutability and mobility, and an infrastructure that provides object interconnectivity, security and persistence. HADAS is fully implemented in Java and comes with a full programming environment for developing and executing network-centric applications.