Semantic Component Composition Joseph R. Kiniry Department of Computer Science California Institute of Technology Mailstop 256-80 Pasadena, CA 91125
[email protected] ABSTRACT General Terms Building complex software systems necessitates the use of specification languages, formal methods, kind theory, reuse, component-based architectures. In theory, of the set of com- glue-code generation, automatic programming, domain-specific ponents needed for a design, only some small portion of languages them are “custom”; the rest are reused or refactored existing pieces of software. Unfortunately, this is an idealized situ- 1. INTRODUCTION ation. Just because two components should work together Modern software systems are increasingly complicated. Com- does not mean that they will work together. bine new technologies, complex architectures, and incredi- ble amounts of legacy code, and you have systems that no The “glue” that holds components together is not just tech- one can even partially comprehend. As complexity rises, nology. The contracts that bind complex systems together code quality drops and system reliability suffers. implicitly define more than their explicit type. These “con- ceptual contracts” describe essential aspects of extra-system Building reliable complex systems necessitates the use of semantics: e.g., object models, type systems, data represen- excellent software engineering practices and tools. But even tation, interface action semantics, legal and contractual obli- with this bag of tricks, the modern software engineer is of- gations, and more. ten overwhelmed with the technological problems inherent in building such complex systems. Most projects have to Designers and developers spend inordinate amounts of time support multiple programming languages and models, deal technologically duct-taping systems to fulfill these concep- with several different architectures (both hardware and soft- tual contracts because system-wide semantics have not been ware), have distributed and concurrent subsystems, and must rigorously characterized or codified.