The Unified Model of Dependability (UMD)

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 stakeholders will focus on different properties of such systems, e.g., continuity, availability, performance, real-time response, ability to avoid catastrophic failures, capability of resisting adverse conditions, and prevention of deliberate privacy intrusions. The concept of dependability enables these various concerns to be subsumed within a single conceptual framework. The polysemous nature of the concept of dependability, however, brings also the risk of creating confusion, making the task of developing dependable systems even more difficult.

The Unified Model of Dependability (UMD) aims to establish a common language for discussing a variety of dependability attributes, and to make them measurable. To capture stakeholders' dependability needs and perspectives, UMD takes into account different aspects of a dependability attribute, including the affected system functionalities, the acceptable manifestation of a specific issue (e.g., a failure or a hazard) or class of issues, the external events (adverse conditions, attacks, etc.) that can create an unreliable system, and the expected system reaction to mitigate the issues impact over the stakeholders.

By providing a structured approach to eliciting and organizing dependability requirements, UMD helps the stakeholders to better express their needs, understand interactions among the dependability attributes, and set the corresponding values.

UMD Tool Description1.pdf    Tech Report CS TR 46011.pdf