Towards a Mobile Code Management Environment for Complex,Real-Time,Distributed Systems

We present a novel mobile code management environment,currently under design and development. Our design employs anopen architecture, suitable for ``plug-and-play' with COTS andother groups' tools. While we have studied new algorithms, costand objective functions, and other fundamental issues, the maincontribution of this experimental research work is in the environmentitself. It should be noted that networked platforms, such asthe World Wide Web, are inherently not suitable for traditional,predictable real-time applications. Thus, real-time concernsnecessarily need to be blended with others concerns, and thetarget applications, making use of our environment, will toobe a blend of partially hard real-time and partially (or mostly)soft-real- time ones. The prototype environment will thereforesupport performance-based analysis and management focusing notonly on predictability but also on compilation, efficiency, safetyand other tradeoffs. We have selected the Java language and itsbytecode format as a representation for mobile code as well asa language for our implementation.     

Statically safe speculative execution for real-time systems

Deterministic worst-case execution for satisfying hard-real-time constraints, and speculative execution with rollback for improving average-case throughput, appear to lie on opposite ends of a spectrum of performance requirements and strategies. Nonetheless, we show that there are situations in which speculative execution can improve the performance of a hard real-time system, either by enhancing average performance while not affecting the worst-case, or by actually decreasing the worst-case execution time. The paper proposes a set of compiler transformation rules to identify opportunities for speculative execution and transform the code. Moreover, we have conducted an extensive experiment using simulation of randomly generated real-time programs to evaluate applicability and profitability of speculative execution. The simulation results indicate that speculative execution improves average execution time and program timeliness. Finally, a prototype implementation is described in which these transformations have been evaluated for realistic applications     

A development environment for complex distributed real-timeapplications

Engineering of complex distributed real-time applications is one of the hardest tasks faced by the software profession today. All aspects of the process, from design to implementation, are made more difficult by the interaction of behavioral and platform constraints. Providing tools for this task is likewise not without major challenges. In this paper, we discuss a tool suite which supports the development of complex distributed real-time applications in a suitable high-level language (CRL). The suite's component tools include a compiler, a transformer-optimizer, an allocator-migrator, a schedulability analyzer, a debugger-monitor, a kernel, and a (simulated) network manager. The overall engineering approach supported by the suite is to provide as simple and natural an integrated development paradigm as possible. The suite tools address complexity due to distribution, scheduling, allocation and other sources in an integrated manner (largely) transparent to the developer. To reflect the needs of propagation of functional and nonfunctional requirements throughout the development process, a number of robust code transformation and communication mechanisms have been incorporated into the suite. To facilitate practical use of the suite, the developed programs compile-transform to a safe subset of C++ with appropriate libraries and runtime support. (In this safe subset (C++) the use of pointers is minimized. Aliases are not allowed