Minds and Machines

, Volume 21, Issue 3, pp 411–430

NO Revision and NO Contraction


DOI: 10.1007/s11023-011-9243-1

Cite this article as:
Wheeler, G. & Alberti, M. Minds & Machines (2011) 21: 411. doi:10.1007/s11023-011-9243-1


One goal of normative multi-agent system theory is to formulate principles for normative system change that maintain the rule-like structure of norms and preserve links between norms and individual agent obligations. A central question raised by this problem is whether there is a framework for norm change that is at once specific enough to capture this rule-like behavior of norms, yet general enough to support a full battery of norm and obligation change operators. In this paper we propose an answer to this question by developing a bimodal logic for norms and obligations called NO. A key to our approach is that norms are treated as propositional formulas, and we provide some independent reasons for adopting this stance. Then we define norm change operations for a wide class of modal systems, including the class of NO systems, by constructing a class of modal revision operators that satisfy all the AGM postulates for revision, and constructing a class of modal contraction operators that satisfy all the AGM postulates for contraction. More generally, our approach yields an easily extendable framework within which to work out principles for a theory of normative system change.


NormsModal logicRevisionContraction

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.CENTRIA—Artificial Intelligence Center, Department of Computer ScienceUniversidade Nova de Lisboa, FCT/UNLCaparicaPortugal