Component-based software structuring principles are now commonplace at the application level; but componentization is far less established when it comes to building low-level systems software. Although there have been pioneering efforts in applying componentization to systems-building, these efforts have tended to target specific application domains (e.g., embedded systems, operating systems, communications systems, programmable networking environments, or middleware platforms). They also tend to be targeted at specific deployment environments (e.g., standard personal computer (PC) environments, network processors, or microcontrollers). The disadvantage of this narrow targeting is that it fails to maximize the genericity and abstraction potential of the component approach. In this article, we argue for the benefits and feasibility of a generic yet tailorable approach to component-based systems-building that offers a uniform programming model that is applicable in a wide range of systems-oriented target domains and deployment environments. The component model, called OpenCom , is supported by a reflective runtime architecture that is itself built from components. After describing OpenCom and evaluating its performance and overhead characteristics, we present and evaluate two case studies of systems we have built using OpenCom technology, thus illustrating its benefits and its general applicability.

Recent research has recognised the potential of coupling ADLs with underlying runtime environments to support systematic and integrated "specification-todeployment" architectures. However, while some promising results have been obtained, much of this research has not considered the crucial issue of causally-connected dynamic reconfiguration and has considered only domain-specific areas. In this paper we discuss a specification-to-deployment architecture called Plastik that employs an extended generalpurpose ADL and is underpinned by an efficient runtime that is suited both for high-level application development and low-level systems development (e.g. embedded systems). Runtime reconfiguration is supported both at the ADL level and at the runtime level, and both programmed reconfiguration and adhoc reconfiguration are supported. The paper focuses on the mapping of ADL-level specifications to runtime instantiations and on the necessary runtime support for causally-connected dynamic reconfiguration.