. In this paper we propose the deontic logic dus, that formalizes reasoning about prescriptive obligations in update semantics. In dus the definition of logical validity of obligations is not based on truth values but on action dynamics. You know the meaning of a normative sentence if you know the change it brings about in the ideality relation of anyone the news conveyed by the norm applies to. 1 The logic of norms One of the first topics discussed in the development of deontic logic was the question whether norms have truth values. For example, Von Wright (1981, 1998) was hesitant to call deontic formulas `logical truths,' because "it seems to be a matter of extralogical decision when we shall say that `there are' or `are not' such and such norms." Alchourr'on and Bulygin discussed the possibility of a logic of norms, which they distinguish from the logic of normative propositions. "One such issue is the problem of the possibility of a logic of norms. Some authors think that there ...

this paper we discuss when and how to use deontic logic in multi agent systems

The deontic logic dus is a deontic update semantics for prescriptive obligations based on the update semantics of Veltman. In dus the definition of logical validity of obligations is not based on static truth values but on dynamic action transitions. In this paper prescriptive prima facie obligations are formalized in update semantics. The logic formalizes the specificity principle, has reinstatement and does not have an irrelevance problem. Moreover, it handles the diagnostic problem by distinguishing

. In this paper we introduce the two-phase deontic logic 2dl. The preference-based semantics of 2dl is based on an explicit preference ordering between worlds, representing different degrees of ideality. The preference ordering can be used in two ways to evaluate formulas, which we call ordering and minimizing. Ordering uses all preference relations between relevant worlds, whereas minimizing uses the most preferred worlds only. We show that ordering corresponds to the inference pattern strengthening of the antecedent and the conjunction rule for the consequent, and minimizing to the inference pattern weakening of the consequent and the disjunction rule for the antecedent. Moreover, we show that in several problems like the notorious contrary-to-duty paradoxes ordering and minimizing have to be combined to obtain the desirable conclusions, and that in a dyadic deontic logic this can only be done in a so-called two-phase deontic logic. In the first phase the preference ordering is const...