Abstract

We present a language framework for describing dependable systems which emphasizes modularity and composition. Dependability and functionality aspects of an application may be described separately providing a separation of design concerns. Futhermore, the dependability protocols of an application may be constructed bottom-up as simple protocols that are composed into more complex protocols. Composition makes it easier to reason about dependability and supports the construction of general reusable dependability schemes. A significant aspect of our language framework is that dependability protocols may be loaded into a running application and installed dynamically. Dynamic installation makes it possible to impose additional dependability protocols on a server as clients with new dependability demands are integrated into a system. Similarly, if a given dependability protocol is only necessary during some critical phase of execution, it may be installed during that period only. 1 Introduc...

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