The component-based software engineering (CBSE)1 methodology has been developed to facilitate the understanding, development, and evolution of large-scale software systems. By emphasizing strong encapsulation of code with well defined interfaces between modules, a component approach provides a way of decomposing software into units that are conceptually manageable, and that interact in specific and easily understood ways.
These characteristics also facilitate the design and evolution of large, complex software systems by distinguishing between the functional specification of a component (fixed or slowly changing) and its implementation (possibly more rapidly changing, or even having multiple implementations). With thoughtful design of interfaces, component approaches can promote software reuse and interoperability. The encapsulation of components makes them useful in collaborative software development situations, where individuals or small groups take responsibility for the implementation of components conforming to interface specifications agreed to by the collaboration as a whole. These characteristics match very well with the way that the modern computational science community approaches simulation software, which makes the component approach an ideal match for high-performance scientific computing. Furthermore, simulation coupling is of rapidly growing importance in scientific computing, and maps directly to the philosophy of software components.
Although the idea of CBSE has a long history, component architectures have only recently become practical for use in high-performance scientific computing. Development of the Common Component Architecture,2 a general component environment, began with the establishment of the CCA Forum3 in 1998. The Cactus framework,4 originally developed primarily to support numerical relativity simulations, began appearing in the scientific literature in roughly 1999. Another domain-specific framework effort, the Earth System Modeling Framework (ESMF),5 6 began in 2001.
Scientific computing poses both technical and sociological challenges to the deployment and adoption of new technologies, such as components and frameworks. The scientific CBSE community is still in the formative stages of understanding how these concepts can be used most effectively in the context of advanced computational science applications. At the same time, the field is evolving: computing power grows, the tools and software environments evolve, and applications move to take advantage of new capabilities not just to solve larger problems faster, but also at higher levels of physical fidelity. If CBSE is to become a routine part of computational science, we need to anticipate emerging trends and how they will impact the concepts and tools of CBSE. These emerging trends in high-end scientific computing pose both challenges and opportunities for component-based software development, and provide incredible opportunities to dramatically enhance the reliability, maintainability, and scope of HPC applications.
