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On the expressive power of primitives for compensation handling

Publication . Lanese, Ivan; Vaz, Cátia; Ferreira, Carla

Modern software systems have frequently to face unexpected events, reacting so to reach a consistent state. In the field of concurrent and mobile systems (e.g., for web services) the problem is usually tackled using long running transactions and compensations: activities programmed to recover partial executions of long running transactions. We compare the expressive power of different approaches to the specification of those compensations. We consider (i) static recovery, where the compensation is statically defined together with the transaction, (ii) parallel recovery, where the compensation is dynamically built as parallel composition of compensation elements and (iii) general dynamic recovery, where more refined ways of composing compensation elements are provided. We define an encoding of parallel recovery into static recovery enjoying nice compositionality properties, showing that the two approaches have the same expressive power. We also show that no such encoding of general dynamic recovery into static recovery is possible, i.e. general dynamic recovery is strictly more expressive.

2010Conference object

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Towards compensation correctness in interactive systems

Publication . Vaz, Cátia; Ferreira, Carla

One fundamental idea of service-oriented computing is that applications should be developed by composing already available services. Due to the long running nature of service interactions, a main challenge in service composition is ensuring correctness of failure recovery. In this paper, we use a process calculus suitable for modelling long running transactions with a recovery mechanism based on compensations. Within this setting, we discuss and formally state correctness criteria for compensable processes compositions, assuming that each process is correct with respect to failure recovery. Under our theory, we formally interpret self-healing compositions, that can detect and recover from failures, as correct compositions of compensable processes.

2009Conference object

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