José Carmo

Deontic Logic and Contrary-to-Duties

Deontic logic is concerned with the logical analysis of such normative notions as obligation, permission, right and prohibition. Although its origins lie in systematic legal and moral philosophy, deontic logic has begun to attract the interest of researchers in other areas, particularly computer science, management science and organisation theory. Among the application areas which have already received some attention in the literature are: issues of knowledge representation in the design of legal expert systems; the formal specification of aspects of computer systems, for instance in regard to security and access control policies, fault tolerance, and database integrity constraints; the formal characterisation of aspects of organisational structure, pertaining for example to the responsibilities and powers which agents are required or authorised to exercise. The “AEON” workshop proceedings provide some illustrations of work in these areas (see [ΔEON91; ΔEON94; ΔEON96]).

A Role Based Model for the Normative Specification of Organized Collective Agency and Agents Interaction

In this article we propose a role based model for the specification of organized collective agency, based on the legal concept of artificial person and on the normative perspective of organizational systems. We focus on the analysis of groups of agents (humans or not) that want to act collectively in a (more or less) permanent basis, and in a stable and organized way, as it is the typical case of organizations. We argue that in those cases such groups of agents should give rise to a new agent, that we call of institutionalized agent, with its own identity, whose structure is essentially defined through the characterization of a set of roles and whose behavior is determined by the acts of the agents that play such roles. We also present a deontic and action modal logic that captures the concept of acting in a role and relates it with the deontic notions of obligation, permission and prohibition. This logic is used in the formal specification of institutionalized agents and of societies of agents and in the rigorous analysis of them. We pay particular attention to the interaction between agents through contracts or other normative relations. A high level specification language is also suggested.

Indirect Action, Influence and Responsibility

In this paper a new action concept is proposed, within the same tradition of the logical characterization of act descriptions as employed by Kanger, Porn and Lindhal. The concept sums up a successful goal oriented social activity into a unique assertion referring to the agent who has initiated it. It is argued that this notion allows us to increase the expressiveness of the characterization of agents’ activity within organizations.

Action concepts for describing organised interaction

The main aim of this paper is to propose a set of action concepts useful for describing organised interaction. These action concepts focus on two distinctions: the distinction between direct and indirect action, and the distinction between successful and not necessarily successful action. The formal characterisation of these concepts is given by means of modal logic, following the same tradition in the logical characterisation of act descriptions as employed by Kanger (1972) and Porn (1970). The modal action operators proposed are also combined with a deontic logic and a conditional logic, in order to illustrate their application to the analysis of some simple organisations. The focus of interest is on the notion of transmission of agency, and on the characterisation of the conditions under which an organisation recognises that an agent has fulfilled the responsibilities assigned to him.

Deontic Logic, Agency and Normative Systems

The Hohfeldian fundamental legal conceptions that deal with solely deontic LEGAL RELATIONS, the duty/privilege and right/no-right pairs, require not only an adequate definition of agency for the person who is obligated or permitted to act, but also the same of patiency for the person to-or-for whom that action is directed. Person-is DUTY to see-to-it-that that state-of-affairs-s is so for the benefit of person-j is defined here in terms of a deontic OBLIGATION operation and DONE-BY (D2) and DONE-FOR (D4) relations between a state of affairs and persons. This paper is a refinement of the authors earlier efforts to modify, extend, and enrich Hohfelds fundamental legal conceptions into a more general notion of LEGAL RELA nONS (defined concepts are expressed in all capital letters.) In particular, the agency concept of DONE-BY is being brought into closer conformity with Belnaps emerging stit logic, with the modifications of deontic logic accompanying such changes. The S4-D2 action modal logic considered here is intended to be a part of the A-HOHFELD logic in which LEGAL RELATIONS are defined and from which a representation language called the A-HOHFELD language is derived. The A-HOHFELD language is being used as a representation language for constructing MINT (Multiple INTerpretation) interpretationassistance systems for helping lawyers to detect alternative structural interpretations of sets of legal rules.

Ockhamist Computational Logic: Past-Sensitive Necessitation in CTL

The framework underlying CTL* is extended in order to include past operators Recent developments in areas related to concurrent program specification and verification, as well as database and information systems specification, justify the interest of such extension The semantics for the language so obtained is defined according to the ockhamist approach to non-deterministic time The differences between this semantics and the original semantics for CTL* are analysed. A sound axiomatization is proposed for such logic and its completeness is proved

Deontic Database Constraints, Violation and Recovery

The paper discusses the potential value of a deontic approach to database specification. More specifically, some different types of integrity constraints are considered and a distinction is drawn between necessary (“hard”) and deontic (“soft”) constraints.Databases are compared with other normative systems. A deontic logic for database specification is proposed and the problems of how to react to, and of how to correct, or repair, a situation which arises through norm violation are discussed in the context of this logic. The limitations of the proposed logic and possible modifications and extensions of it are analysed.

A New Approach to Contrary-to-Duty Obligations

Since the publication of (Chisholm, 1963), deontic logicians have struggled with the problem of supplying an adequate formal characterisation of the distinction between primary obligations and those obligations — called “contrary—to—duty” by Chisholm — which come into force when some other obligation is violated.

Completeness and decidability results for a logic of contrary-to-duty conditionals

This article has two parts. In Part I, we briefly outline the analysis of ‘contrary-to-duty’ obligation sentences presented in our 2002 handbook chapter ‘Deontic logic and contrary-to-duties’, with a focus on the intuitions that motivated the basic formal-logical moves we made. We also explain that the present account of the theory differs in two significant respects from the earlier version, one terminological, the other concerning the way the constituent modalities interconnect. Part II is the principal contribution of this article, in which we show that it is possible to define a complete and decidable axiomatization for the Carmo and Jones logic, a problem that was still open. The axiomatization includes two new inference rules; we illustrate their use in proofs, and show that on the basis of this axiomatization we can recover all the axioms and rules considered in ‘Deontic logic and contrary-to-duties’, and used there in the analysis of contrary-to-duty conditional scenarios.

Collective agency, direct action and dynamic operators

We review the stit semantic framework and the main stit operators that have been proposed by Belnap, Perloff and Horty (among others), a theory that has recently attracted the attention of the multiagent community. We discuss the problem of how to model the notion of collective agency, both in the sense of a joint action of a group of agents and as the agency of collective entities, like organisations. We show how we can define the direct and immediate effects of agents’ actions, both in the achievement sense and in the deliberative sense, without any assumptions on the nature of time and considering the particular case of a discrete time. Finally, we also show how we can define a kind of dynamic logic operator that allows us to express what would obtain, if a direct ‘‘sees to it’’ action is performed, seeing it as a particular case of formulae of the form [a: ϕ]�, that have the following informal meaning: ‘‘if agent a selects an action that leads to the truth of ϕ, after such action is performed, � is the case’’ (or, simply, ‘‘after a choosing ϕ, � is the case’’).