An Ontological Approach to Support Dysfunctional Analysis for Railway Systems Design

Dysfunctional analysis is an essential and demanding task in the early development stages of safety-critical systems (SCSs). Nevertheless, current practices present several drawbacks. Generally, a common dysfunctional analysis conceptualization is missing and it is dependent on safety analysis techniques. Moreover, some safety analysis methods require well-known system behaviors expressed by dynamic models such as sequence diagrams and finite automata. However, the dynamic character of these models increases their susceptibility to changes and then they are not obtainable in the early design stages. Since dysfunctional analysis highly relies on the experience of safety analysts and the feedback (REX) obtained from previous systems development, there is a need to formalize this knowledge domain in a structured way to ensure its future reuse. Furthermore, safety measures derived from this dysfunctional analysis approach must be strongly linked to a goal-oriented perspective and adapted to a specific context. For this purpose, this paper presents a real-world semantics interpretation and conceptualization of dysfunctional analysis related concepts based on the Unified Foundational Ontology (UFO) and well-known standards to avoid ambiguities. The proposed Dysfunctional Analysis Ontology (DAO) aims to provide a systematization of the goal-oriented dysfunctional analysis through a terminological clarification in order to prevent hazards in the first design phases. Then, a DAO formalization is proposed using the Web Ontology Language (OWL). Finally, the DAO pattern is applied to two different real critical scenarios from the railway domain in order to illustrate and evaluate this ontological approach.