Proposed new definitions for safety (Draft)

 The following definitions were proposed at the recent Dagstuhl workshop and will be incorporated in an upcoming Safecomp paper.

These below text is hereby placed in the public domain, with a specific objective of being incorporated into safety standards.

 ·     Loss: an adverse outcome, including damage to the system itself, negative societal externalities, damage to property, damage to the environment, injury or death to animals, and injury or death to people

Note: This is broader in scope than other typical definitions of loss or harm. Some types of loss might be assigned very low severity in some application domains. Allocation of blame does not affect whether a loss occurred.

 ·     Risk: combination of the probability of occurrence of a loss, or pattern of losses, and the importance to stakeholders of the associated consequences

Note: Net importance can be non-linearly related to individual losses if forming a pattern. Correlated loss events, inequitable loss patterns, and loss patterns involving a failure to mitigate emergent loss trends are included.

 ·     Safety constraint: a limitation imposed on risk by stakeholder requirements

Note: This implicitly requires identification of stakeholders who might be affected by losses, and makes it more straightforward to view safety as a multi-dimensional constrained optimization problem rather than a mostly one-dimensional pure risk optimization problem [Koopman24b]. Safety constraints might include: limits on individual risks, limits on net risk, and exposure limits for specified types of risk patterns, even if risk pattern constraints worsen net risk.

 ·     Acceptable: meets all safety constraints

Note: The phrase “acceptably safe” might be used in some contexts. While “Safety” is defined below, use of the word “safe” alone should be avoided.

 ·     Safety case: structured argument, supported by a body of evidence, that provides a compelling, comprehensible and valid case as to whether or not a system meets a comprehensive set of safety constraints

Note: This emphasizes meeting constraints rather than a threshold for net risk. A net risk threshold might be included as one of many constraints.

 ·     Safety engineering: a methodical process of ensuring a system meets all its safety constraints throughout its lifecycle, typically involving hazard analysis, risk assessment, risk mitigation, and continuing safety validation that align with a defined safety case

Note: Addresses constraints, lifecycle, and requirement for a safety case.