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Abstract. The work in this paper 1 is devoted to the definition of a dependability modeling and model based evaluation approach based on UML models. It is to be used in the early phases of the system design to capture system dependability attributes like reliability and availability, thus providing guidelines for the choice among different architectural and design solutions. We show how structural UML diagrams can be processed to filter out the dependability related information and how a system-wide dependability model is constructed. Due to the modular construction, this model can be refined later as more detailed information becomes available. We discuss the model refinement based on the General Resource Model, an extension of UML. We show that the dependability model can be constructed automatically by using graph transformation techniques. 1

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The General Packet Radio Service (GPRS) extends the Global System Mobile Communication (GSM), by introducing a packet-switched transmission service. This paper analyses the GPRS behavior under critical conditions. In particular, we focus on outages, which significantly impact the GPRS dependability. In fact, during outage periods the cumulative number of users trying to access the service grows proportionally over time. When the system resumes its operations, the overload caused by accumulated users determines a higher probability of collisions on resources assignment and therefore a degradation of the overall QoS. This paper adopts a Stochastic Activity Network modeling approach for evaluating the dependability of a GPRS network under outage conditions. The major contribution of this study lies in the novel perspective the dependability study is Corresponding author- 1-framed in. Starting from a quite classical availability analysis, the network dependability figures are incorporated into a very detailed service model that is used to analyze the overload effect GPRS has to face after outages, gaining deep insights on its impact on user’s perceived QoS. The result of this modeling is an enhanced availability analysis, which takes into account not only the bare estimation of unavailability periods, but also the important congestion phenomenon following outages that contribute to service degradation for a certain period of time after operations resume.

The paper presents techniques to support the dependability modeling and analysis of distributed object-oriented applications that are designed according to the Fault Tolerant CORBA (FT-CORBA) specification.

olution and verification of product and process designs. The quality of a product design depends on the quality of the process that produces it. Manufacturers must verify the qualities of both product and process design; the product-in-aprocess approach is an evolutionary one that must account for changes and modifications. . An integrated and best-balanced set of product and process designs. Integration and balance of these items are crucial points. Providing these qualities requires some sort of verifiable compositionality property of components that contributes to the system 's total quality from the viewpoints of Andrea Bondavalli Alessandro Fantechi University of Firenze Diego Latella Luca Simoncini CNUCE Institute EMBEDDED COMPLEX SYSTEMS REQUIRE AN INTEGRATED AND BEST-BALANCED SET OF COMPONENTS. TO USE THESE COMPONENTS REQUIRES SOME SORT OF VERIFIABLE COMPOSITIONALITY, A CONCEPT THAT IMPLIES THE PRESERVATION OF PROPERTIES AND THE ABILITY TO VERIFY THEM. 0272-1732/01/$10

Participant(s): All partners Work package contributing to the deliverable: WP2 Nature: Version: 2.0

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This deliverable deals with the modelling and analysis of interdependencies between critical infrastructures, focussing attention on two interdependent infrastructures studied in the context of CRUTIAL: the electric power infrastructure and the information infrastructures supporting management, control and maintenance functionality. The main objectives are: 1) investigate the main challenges to be addressed for the analysis and modelling of interdependencies, 2) review the modelling methodologies and tools that can be used to address these challenges and support the evaluation of the impact of interdependencies on the dependability and resilience of the service delivered to the users, and 3) present the preliminary directions investigated so far by the CRUTIAL consortium for describing and modelling interdependencies.