After having discussed the general approach of fault-tolerance languages and their main features, the focus is now set on one particular case: The ARIEL1 recovery language. It is also described as an approach towards resilient computing based on ARIEL and therefore dubbed the “recovery language approach” (ReL). In this chapter, first the main elements of ReL are introduced in general terms, coupling each concept to the technical foundations behind it. After this a quite extensive description of ARIEL and of a compliant architecture are provided. Target applications for such architecture are distributed codes, characterized by non-strict real-time requirements, written in a procedural language such as C, to be executed on distributed or parallel computers consisting of a predefined (fixed) set of processing nodes. The reason for giving special emphasis to ARIEL and its approach is not in their special qualities but more on the fact that, due to the first-hand experience of the author, who conceived, designed, and implemented ARIEL in the course of his studies, it was possible for him to provide the reader with what may be considered as a sort of practical exercise in system and fault modeling and in application-level fault-tolerance design, recalling and applying several of the concepts introduced.
The Ariel Recovery Language
This section casts the basis of a general approach in abstract terms, while a particular instance of the herein presented concepts is described in Section 3 as a prototypic distributed architecture supporting a fault-tolerance linguistic structure for application-level fault-tolerance. System and fault models are drawn. The approach is also reviewed with respect to the structural attributes (SC, SA and A) and to the approaches presented in Chapter III, V, and VI. The structure of this section is as follows:
Models are introduced in Sect. 2.1.
Key ideas, concepts, and technical foundations are described in Sect. 2.2.
Section 2.4 shows the workflow corresponding to using RεL.
Sect. 2.5 summarizes the positive values of the structural attributes SA, SC, and A for RεL.