Dynamic Deployment of Executing and Simulating Software Components

Physical boundaries have caused software systems to become less monolithic and more distributed. The trend is progressing to a point where software systems will consist of numerous, loosely-coupled, heterogeneous software components. Increased software dynamism will allow these components to be composed, interchanged, upgraded, or even moved without shutting down the system itself. This form of dynamism is already well-supported through new programming constructs and support libraries (i.e., late binding, introspection); however, we are currently ill-equipped to analyze and simulate those kinds of systems. This paper demonstrates that software dynamism requires not only new modeling constructs but also new simulation environments. While in the past, simulation merely mimicked some real-world behavior, we argue that in the future it will become necessary to intertwine the model world with the real world. This will be essential but not limited to cases where (1) one has incomplete access to models (i.e., proprietary COTS components), (2) it is too expensive to model (i.e., Internet as a connector between software components), or (3) one has not complete faith in models (i.e., legacy components). This paper presents our approach to the concurrent execution and simulation of deployed software components. It will also discuss key differences to “traditional” simulation, emulation, and other similar concepts that are being used to integrate the model world with the real world. 1 Dynamism in Today’s World Today, systems are dynamic entities. A modern CPU can reduce its processor power to conserve energy when its energy supply (i.e., battery) is low. A cell phone adapts to different geographical zones (environments) it is taken into. Examples like these show that systems adapt dynamically to their environment or that systems adapt to dynamic environments. There are many reasons why such dynamic behavior is beneficial but the primary reason is that systems continue to operate even if their surroundings vary or are not as expected. Although it is as much software as it is hardware that gives systems their flexibilities, it is still not often possible to take “pieces of software systems” during run-time and manipulate them. We believe that this will change in the future. Existing technology, such as late binding between software components, already makes it possible to Proceedings of the 2 IFIP/ACM Working Conference on Component Deployment (CD), Edinburgh, Scotland, UK, May 2004, pp. 113-128