Severity-Sensitive Robustness Analysis in Normative Systems

Abstract

Norms specify ideal behaviour. Agents, however, are autonomous, and may fail to comply with the ideal. Contrary to Duty obligations can be used to specify reparational behaviour that mitigates the effects of a violation. In addition to specifying reparational behaviours, it is important to understand how robust a system is against possible violations. Depending on what kind of system property we want to preserve, non-compliance with different norms may be of varying severity. We propose a method for analysing robustness of normative systems, with support for Contrary to Duty obligations. We introduce violation severity as a concept orthogonal to reparational behaviour and specify it by means of a partial order over norms. We use this severity partial order, together with normative specifications, to rank the possible worlds from the most to the least compliant. In this way, we are able to use model checking to analyse robustness to a certain severity, or whether it is possible to achieve a certain goal, without violating any norm of a given severity.

CÒIR: Verifying Normative Specifications of Complex Systems

“…Moreover, by implementing our system in Maude, we obtain a specification which is executable and on which we can perform formal verification using the Maude Linear Temporal Logic (LTL) model checker. In this way we can: (i) Validate our normative specification; for example by verifying that a specified non compliant behaviour always results in a detected violation; and (ii) Verify how robust a multi-agent system is to violations; for example by verifying if a certain property is guaranteed under certain compliance assumptions [1,8].…”

“…Although such analyses are of benefit, for safety critical systems it is important to analyse the interactions between normative constraints and agents' actions as a system evolves. For these reasons the use of model checking [3] techniques to analyse liveness and safety properties of norm-governed systems has been explored [1,6,8]. To date, however, this research has focussed on restricted representations of norms such as labelling states or transitions as compliant/noncompliant.…”