| Web services provide a standard means to achieve interoperability between different software applications in a heterogeneous distributed environment. The Web Services Resource Framework (WSRF) has redefined Grid computing standards, making Web services more suitable for Grid applications by adding persistent state management. A primary benefit of Web and Grid services is that they provide a uniform implementation-independent mechanism for accessing distributed services. However, it is still difficult to build, deploy, and evolve such services. Different Web or Grid services containers are implemented in different programming languages, with different constraints and requirements placed on the programmer. The research described in this dissertation takes a significant first step toward "write-once deploy-anywhere" Web and Grid services, by enabling mobile code for different Web and Grid services containers. The term "mobile code" refers to passive code segments that can be dynamically deployed into a variety of hosting environments. The basis of this approach is the design and definition of a common intermediate language, called X#, for the representation and transmission of mobile code. Three Web services containers (namely, Tomcat, ASP.NET and a gSOAP based C++ container), and two Grid services containers (namely, GT4 and WSRF.NET) now support dynamic mobile code deployment through a standard Web service deployment interface. Containers receive the mobile X# code and then generate container-specific native code in different languages, without exposing these details to applications and Grid services programmers. The dynamically deployed mobile code can access state managed by the hosting container, can utilize functionalities exposed by statically deployed services, and can communicate with other mobile code modules, running either in the same container or in different containers. A performance study shows that the newly deployed mobile code can run as nearly efficiently as it would if it had been deployed statically, through container-specific mechanisms. The resulting software systems enable uniform dynamic deployment of the same code into several different containers written in different languages, including C#, Java, and C++. This reduces the burden on service programmers, facilitates interoperability, and potentially increases the impact of service code by allowing it to run in a larger number of different containers. |
