The termresiliencyhas been used in many fields like child psychology, ecology, business, and several others, with the common meaning of expressing the ability to successfully accommodate unforeseen environmental perturbations or disturbances. The adjectiveresilienthas been in use for decades in the field of dependable computing systems however essentially as a synonym of fault-tolerant, thus generally ignoring the unexpected aspect of the phenomena the systems may have to face. These phenomena become of primary relevance when moving to systems like the future large, networked, evolving systems constituting complex information infrastructures - perhaps involving everything from super-computers and huge server ldquofarmsrdquo to myriads of small mobile computers and tiny embedded devices, with humans being central part of the operation of such systems. Such systems are in fact the dawning of the ubiquitous systems that will support Ambient Intelligence. With such ubiquitous systems, what is at stake is to maintain dependability, i.e., the ability to deliver service that can justifiably be trusted, in spite of continuous changes. Therefore the termresilienceandresilientcomputingcan be applied to the design of ubiquitous systems and defined as the search for the following property:thepersistenceofservicedeliverythatcanjustifiablybetrusted,whenfacingchanges. Changes may be of different nature, with different prospect and different timing. Therefore the design of ubiquitous systems requires the mastering of many, often separated, engineering disciplines that span from advanced probability to logic, from human factors to cryptology and information security and to management of large projects. From an educational point of view, very few, if any, Universities are offering a comprehensive and methodical track that is able to provide students with a sufficient preparation that makes them able to cope with the challenges posed by the design of ubiquitous systems. In Europe an activity has started towards the identification of a MSc curriculum in Resilient Computing as properly providing a timely and necessary answer to requirements posed by the design of ubiquitous systems. To this aim, a Network of Excellence ReSIST - Resilience for Survivability in IST-was run from January 2006 to March 2009 (see http://www.resist-noe.org). In this presentation the results of ReSIST will be presented as well as the identified MSc curriculum in Resilient Computing, to share its experience and to involve a much larger, open and qualified community in the discussion of the proposed curriculum.

System Dependability is the greatest challenge facing us before we can realise the potential of the Information Society in the 21 century. Unless we can build systems that we can trust to behave as we intended them to, we cannot risk creating a society where our economic well-being, our quality of life, our safety and our security depend on the correct and continuous interactions of millions of computer-based systems.

This paper presents an approach for the specification and the verification of the correctness of fault tolerant system designs achieved by the application of fault tolerant techniques. The approach is based on process algebras, equivalence theory and temporal logic. The behaviour of the system in the absence of faults is formally specified and faults are assumed as random events which interfere with the system by modifying its behaviour. The fault tolerant technique is formalized by a context that specifies how replicas of the system cooperate to deal with faults. The system design is proved to behave correctly under a given fault hypothesis by proving the observational equivalence between the system design specification and the fault-free system specification. Additionally, model checking of a temporal logic formula which gives an abstract notion of correct behaviour can be applied to verify the correctness of the design. The opportunities given by the expression of the fault hypothesis using temporal logic are discussed. The actual usability of the approach in real case studies is supported by the availability of automatic tools for equivalence checking and for proving the temporal logic properties by model checking.

Computer controlled systems are used in many fields of applications, with different levels of criticality requirements. A common characteristic of such systems is the increasing complexity in intrinsic terms (management of distribution, redundancy, layering of functionalities, etc.) and of the in-the-field operation (interfaces towards the environment, timing constraints, criticality of the controlled applications, etc.). This increasing complexity rarely can be completely mastered and usual design practices often suffer from partial approaches, overlooked details, inadequate modeling, insufficient prototyping, limited design tools or techniques available; not to deal with incorrect or incomplete or not understood user requirements, which are often the cause of the final failure of a design or system.

The paper presents an approach for the specification and verification of the correctness of dependable system designs achieved by the application of fault tolerant techniques based on equivalence relations and model checking techniques. The behaviour of the system in absence of faults is formally specified and faults are assumed as random events which interfere with the system by modifying its behaviour. The fault tolerant technique is formalized by a context, which specifies how replicas of the system cooperate to deal with faults. The system design is proved to satisfy the correctness property under a given fault hypothesis, by proving the observational equivalence between the system design specification and the fault free system specification. Additionally, model checking of a temporal logic formula which gives an abstract notion of correct behaviour can be applied to verify the correctness of the design.

The authors propose the use of a functional language and of a dataflow computing model for the design of large-scale parallel computing systems for which dependability, in its aspects of reliability, timeliness, parallelism, and distributedness, is the requirement of main concern. The design methodology is sufficiently flexible to allow for verification and validation of such systems from the very first steps of the design. The advantages of such an approach reside in the potential for parallelism it admits, in being characterized by referential transparency, and in the property of composability. The design description language is extended for dealing with dependability issues, with the creation of a library of fault tolerance schemes which can be used for modular insertion of redundancy. A set of tools is being defined as part of a design development environment allowing the designer to proceed in successive interactive steps, each of which can be validated.>

The use of dataflow-like models for the in-the-large design of real-time applications is discussed. In these models, modules can only communicate by (asynchronously) receiving messages when activated and transmitting result messages when terminating. This rather restrictive computational model allows the description of typical, cyclic control programs, with predictable, well-verifiable behavior. In particular, important timing properties can be dealt with in the in-the-large design. The case for the use of dataflow-like models is outlined, and the choice of appropriate notations, which implies a tradeoff between predictability of behavior and expressive power, and the potential for an advanced design support environment are discussed.>

The advent of microprocessors as low-cost general- purpose computing elements has made feasible the implementation of multiprocessor systems containing a large number of cooperating modules. When the number of modules in the system is large it is unlikely that all of them are busy with computation at all times. Therefore, it may be possible to utilize this "slack" by having the nonbusy modules perform diagnostics. In this way computation and diagnosis are performed concurrently in real time. In this correspondence we consider the problem of designing systems in which concurrent computation/diagnosis is possible and we evaluate the potential of such approach.

A new approach to the problem of diagnosability with repair of digital systems composed of n units, of which at most t are faulty, is introduced.