GUARDS Home Page | Internal Reports | Team Directory

• Genericity and Upgradability in Ultra-Dependable Real-Time Architectures (compressed postscript - 98 Kb) (postscript - 282 Kb)

Andy Wellings, Ljerka Beus-Dukic, Alan Burns, David Powell

A version of this paper was presented at Real-Time Systems Symposium 1996 (Work in Progress) held in December 1996, Washington, USA.

Abstract. We report on the ideas currently being developed within the European GUARDS project to develop a generic upgradable architecture for real-time dependable systems. After a brief introduction and overview of the architecture, we outline the GUARDS approach for scheduling real-time replicated computation.

• Ultra-Dependable and Real-Time Systems: The GUARDS Approach

David Powell, Jean Arlat, Ljerka Beus-Dukic, Andy Wellings, Andrea Bondavalli, Felicita Di Giandomenico

The paper was presented at CaberNet Network of Excellence 3rd Plenary Workshop, March 1997.

• GUARDS Generic Upgradable Architecture for Real-Time Dependable Systems

Christophe Rabejac, Herve Schindler

Data Systems in Aerospace, May 1997.

• Discriminating Fault Rate and Persistency to Improve Fault Treatment

Andrea Bondavalli, Silvano Chiaradonna, Felicita Di Giandomenico, Fabrizio Grandoni

27th IEEE Fault-Tolerant Computing Symposium, 24-27 June 1997, Seattle, Washington, USA.

Abstract. In this paper the consolidate identification of faults, distinguished as transient or permanent/intermittent, is approached. Transient faults discrimination has long been performed in commercial systems: threshold-based techniques have been practiced for several years for this purpose. The present work aims to contribute to the usefulness of the count-and-threshold scheme, through the analysis of its behaviour and the exploration of its effects on the system. To this goal, the scheme is mechanized as a device named a-count, endowed with a few controllable parameters. a-count tries to balance between two conflicting requirements: to keep in the system those components that have experienced just transient faults; and to remove quickly those affected by permanent or intermittent faults. Analytical models are derived, allowing detailed study of a-count's behaviour; the actual evaluation, in a range of configurations, is performed by standard tools, in terms of the delay in spotting faulty components and the probability of improperly blaming correct ones.

Keywords: Fault Persistency Discrimination, Fault Treatment, Scoring Functions, Threshold-based Identification, Modelling and Evaluation.

• Analytical Modelling and Evaluation of Phased-mission Systems for Space Applications

Andrea Bondavalli, Ivan Mura, Manuela Nelli

2nd IEEE HASE Workshop on High Assurance Systems Engineering, 11-12 August 1997, Washington DC, USA.

Abstract. This paper deals with the modelling and evaluation of mission-phased systems devoted to space applications. We propose a two level hierarchical method that allows to model such systems and to master the complexity of the analysis. Our approach considers a separate modelling and resolution of the phases, and of the dependencies among phases caused by the usage of the same system components in the different phases. Moreover, it accounts for a dynamic choice on whether some phases have to be skipped. The proposed method turns out in a great flexibility, easy applicability and reusability of the defined models. Furthermore, it permits not only to obtain information on the overall behaviour of the system, but also at the same time to focus on each single phase and hence allows to detect system dependability bottle-necks.

• GUARDS - Generic Upgradable Architecture for Real-Time Dependable Systems (postscript - 286Kb)

Cristophe Rabejac, Herve Schindler

DAta Systems In Aerospace - DASIA'97, 26-29 May 1997, Seville, Spain.