The objective of this proposed research is to develop a semantic foundation for semantic composition and interoperation of heterogeneous components of open systems. Composition and interoperation occur at many levels (requirements, specification, code, executables) and along multiple dimensions (functionality, reliability, security, availability). Relations among the various levels and dimensions must be preserved. Existing work on composition and interoperation has largely focused on syntactic structure. It is essential to develop a semantic basis in order to provide for safe, secure, and meaningful combinations. Semantic structuring of complex systems should provide a firm basis for determining what parts are interchangeable under given conditions, and to predict effects of changes: of components on the whole, and of system requirements on requirements for the parts. There is a wide range of applications where such a semantic foundation for interoperation can be of value. It is especially important in applications that combine components from diverse domains such as: data bases, spread sheets, knowledge bases, multi-media, mobile-agents, control theory, or event-based simulations. Metalogical methods from the theory of general logics, and associated techniques of mappings in and across formalisms, are used to achieve formalism-independent semantics for system composition. This supports the multidimensionality of a system's levels of description and formalization. Techniques from the theory of Open Mechanized Reasoning Systems (OMRS) as well as work on the formal semantics of actor systems are used to study interoperation aspects. Reflective techniques, particularly reflective logics and multi-model systems are employed extensively. This research is expected to lead to a new technology for composition, interoperation and dynamic evolution of software systems. It seeks to treat interoperability at many levels and along many dimensions: components, languag es, specifications, formalisms/logics, and tools. This provides the capacity to move in a mathematically rigorous way across the different formalizations of a system, and to use the different tools supporting these formalizations in a rigorously integrated way. The research is based on two key technical ideas: module calculi (for integration) and open multi-model systems (for interoperation). The module calculus is formalism-independent, and is intended to have powerful new operations such as generalization. Open multi-model systems formalize the multidimensional aspects of independent interoperating parts. ***
