Reliable computer systems used in the telecommunication industry, in cars and automated factories (process control) are often implemented as special purpose systems which are vendor-specific, expensive, hard to maintain and difficult to upgrade. Often, those systems apply proprietary techniques to achieve security and predictable timing behavior, even in case of faults. With the need of integrating multiple of those control systems into a bigger whole, requirements arise to open up proprietary systems for standard (non real-time) distributed computing technology.

Component-oriented programming provides a promising way to system composition out of units with contractually specified interfaces and explicit context dependencies. Software component can be deployed independently, they are subject to composition by third parties. There exist a number of distributed component frameworks, notably the Common Object Request Broker Architecture (CORBA) [14] , Microsoft’s Distributed Component Object Model (DCOM/COM+) [4] , SUN’s JavaBean Model [7] , and the relatively new .NET framework.

Although all of these frameworks simplify the implementation of complex, distributed systems significantly, the support of techniques for reliable, fault-tolerant, and secure software, such as group communication protocols or replication is very limited. Any fault tolerance extension for components needs to trade off data abstraction and encapsulation against implementation specific knowledge about a component’s internal timing behavior, resource usage, interaction and access patterns. These non-functional aspects of a component are crucial for the predictable behavior of real-time and fault-tolerance mechanisms. However, in contrast to the various mechanisms describing a component’s functional interface (Interface Definition Languages, Class/Method specifications), there is no general means to describe a component’s non-functional properties, such as security settings, fault-tolerance measures and timing behavior.

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