Non-Functional Norms Specification and Verification Approach for Normative Multi-agents Systems

Normative Multi-agent system (NMAS) forms a promising approach to software engineering for the development of autonomous systems, in norms-based environments. During the construction of these systems, different requirements can be considered: functional and non-functional requirement. Existing research in NMAS have mostly focused on the study of functional and behavioral requirements specification and verification, while Non-Functional Requirements (NFR) are crucial in the development of systems. They have dealt with the NFR implicitly through the capabilities of functional requirements. An important research issue refers to NFR in NMAS, i.e. how to specify and enforce NFR in NMAS that involves heterogeneous and autonomous agents. The NFR define constraints for the system and specify the qualities that a system can have, for example, security, performance, reliability, comfort, availability. Also, NFR might conflict among each other (for example, cost and quality, comfort and economy). A conflict between two NFR occurs when the fulfillment of one NFR violates another NFR. One of the main challenges currently faced in NMAS research is that of NFR specification and verification. In particular, how to specify and verify NFR in autonomous systems? In this paper, we propose a normative approach that allows the specification and verification of NFR for autonomous systems. To do this, we propose a new type of norms, called Non-Functional Norms (NFN). Indeed, our approach provides (i) a BNF normative language for specifying NFN, and (ii) a mechanism, based on Constraint Satisfaction Problem (CSP) technique, for the detection and resolution of normative conflicts. Our normative approach is also illustrated by a case study describing Smart City Management System (SCMS).