High Dependability Computing Program Modeling Dependability(5)

Individuals and organizations increasingly use sophisticated software systems from which they demand great reliance. “Reliance ” is contextually subjective and depends on the particular stakeholder’s needs; therefore, in different circumstances, the sta

The success of the program depends on the synergic collaboration of all these actors. It would be valuable to have a common and operational definition of dependability that allows:

The system users to express their needs (i.e. build a precise dependability model

of the required system), in such a way that can be understood, and eventually addressed by the others;

The system developers to clearly compare what they are delivering with what

requested by the users;

The technology researchers/developers to make explicit their goals in terms of the

impact of their technology over dependability;

The empirical researchers to measure, and make explicit what is achievable and

what has been achieved. For example, the gap between users’ demands and developers’ products, or between technology developers’ claims and actual technologies performances. This means to be able to identify the “good” practices and support their transfer.

Many definitions of dependability have been provided in the literature, see for example [1,7,8,9,11]. However, they are mostly general and qualitative. It may not be possible to find a common and operational definition of dependability. To be operational, in fact, a definition needs to be strictly related to the specific context it refers to (the project and its stakeholders). For this reason, we have adopted an alternative approach. Rather than stating yet another definition of dependability, we are identifying a framework for modeling dependability that the different actors could adopt as a common language, enabling them to communicate and understand each other’s needs.

Figure 1. A framework to foster cooperation

This paper is organized as follows. Section 2 introduces the Unified Model of Dependability (UMD), by illustrating its underlying concepts. It discusses its robustness, and shows how UMD can be used to capture the users’ dependability needs (or more precisely the stakeholders’ needs [18]), to build dependability models of individual