Dynamic Migration of Object Semantics among Heterogeneous Environments

The migration of software entities between information systems has been studied mainly in the context of process migration between nodes of distributed operating systems and to lesser extent as object migration between programming environments. Most existing approaches assume homogeneous systems as a prerequisite to migration, despite the fact that heterogeneous hardware, operating systems and programming languages are the norm in most practical environments today. This work is concerned with migration in the context of heterogeneity and focuses on the migration of atomic objects between heterogeneous language environments. A characterization of object migration provides for the first time a coherent context for the comparison of different existing migration systems and discusses the possible levels of and alternative approaches to heterogeneous migration. This analysis leads to the development of a novel migration mechanism capable of transferring the state and behavior of atomic language objects between heterogeneous environments using only limited knowledge about the destination environments. The mechanism migrates a set of related objects as well as their semantics. The design of this mechanism called Heterogeneous Language Migration (HLM) takes a pragmatic approach guided by a set of objectives and is restricted to a defined set of language concepts. Details of its architecture, abstractions, algorithms, representation formats and programming interfaces are described and discussed. The feasibility of this approach is shown in a prototypical implementation and demonstrated in a working example. In contrast to other related approaches, as for example the Java application environment, the HLM migration mechanism is able to handle not only different hardware and operating system platforms but also heterogeneous language environments as well as differences of libraries and applications. The HLM migration mechanism is intended to work without changes to the definitions of objects during migration and without changes to the programming environments involved prior to migration. As a consequence applications need to be designed for migration. Tools that aid in the development of applications for this migration mechanism are proposed. The range of enhancements that can be used to augment the HLM migration mechanism is discussed as well as possible extensions that diverge from the objectives of the pragmatic approach. The necessary support for additional language concepts and the applicability of the HLM migration mechanism to existing language environments are discussed as well. Some examples of possible applications of heterogeneous object migration illustrate the potential advantages of the HLM migration mechanism in practical situations and innovative usage areas. A summary of the achieved results and a perspective of promising future research directions conclude this work.