Heinz W. Schmidt

Reasoning about concurrent objects

Embedded specifications in object-oriented (OO) languages such as Eiffel and Sather are based on a rigorous approach towards validation, compatibility and reusability of sequential programs. The underlying method of design-by-contract is based on Hoare logic for which concurrency extensions exist. However concurrent OO languages are still in their infancy. They have inherently imperative facets, such as object identity, sharing, and synchronisation, which cannot be ignored in the semantics. Any marriage of objects and concurrency requires a trade-off in a space of intertwined qualities. The paper summarises our work on a type system, calculus and an operational model for concurrent objects in a minimal extension of the Eiffel and Sather languages (cSather). We omit concurrency control constructs and instead use assertions as synchronisation constraints for asynchronous functions. We show that this provides a framework in which subtyping and concurrency can coexist.

Runtime verification of timing and probabilistic properties using WMI and .NET

Reliability and availability are key issues to distributed service-oriented systems. We present a methodology for run-time verification of reliability and availability properties for distributed architectures. Our approach generalizes the concept of design-by-contract to contracts involving time and probabilities. We define a language for contracts based on probabilistic real time computational tree logic (PCTL). We provide a formal semantics for this language based on possible execution traces of a system. Then we describe a .NET-based system for monitoring contracts, built upon the Windows Management Instrumentation (WMI) framework.

Shared XML documents in service centers of the future

Call centers are at the core of todays customer relations management. Increasingly, they are also utilized internally as competence and knowledge centers. Turning them into service centers of the future (SCotF) requires parallel communication over several channels, including Internet services, in a distributed synchronous fashion. In this paper, we show that the emerging XML standards provide a good basis for this type of interaction. In turning e-service into a groupware application, we propose to apply a spatial awareness model to assist in the collaboration. We demonstrate that it can be integrated into the XML/XSL-framework. The results are compared with a previous solution, which applied proprietary tools. Questions of fidelity and a critique of the existing standards and tools complement the practical results.