$\mathcal R\!\raise2pt\hbox{$\varepsilon$}\!\hbox{$\mathcal L$}$: A Fault Tolerance Linguistic Structure for Distributed Applications

The embedding of fault tolerance provisions into the application layer of a programming language is a non-trivial task that has not found a satisfactory solution yet. Such a solution is very important, and the lack of a simple, coherent and effective structuring technique for fault tolerance has been termed by researchers in this field as the "software bottleneck of system development". The aim of this paper is to report on the current status of a novel fault tolerance linguistic structure for distributed applications characterized by soft real-time requirements. A compliant prototype architecture is also described. The key aspect of this structure is that it allows to decompose the target fault-tolerant application into three distinct components, respectively responsible for (1) the functional service, (2) the management of the fault tolerance provisions, and (3) the adaptation to the current environmental conditions. The paper also briefly mentions a few case studies and preliminary results obtained exercising the prototype.