An Update Semantics for Defeasible Obligations

arXiv.org Artificial Intelligence

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 defeasible obligations are formalized in update semantics and the diagnostic problem of defeasible deontic logic is discussed. Assume a defeasible obligation `normally A ought to be (done)' together withthe fact `A is not (done).' Is this an exception of the normality claim, or is it a violation of the obligation? In this paper we formalize the heuristic principle that it is a violation, unless there is a more specific overriding obligation. The underlying motivation from legal reasoning is that criminals should have as little opportunities as possible to excuse themselves by claiming that their behavior was exceptional rather than criminal.


Aggregative Deontic Detachment for Normative Reasoning

AAAI Conferences

Aggregative deontic detachment is a new form of deontic detachment that keeps track of previously detached obligations. We argue that it handles iteration of successive detachments in a more principled manner than the traditional systems do. To study this new form of deontic detachment, we introduce a 'minimal' logic for aggregative deontic detachment, and we discuss various properties of the logic.


A Modal Characterization of Defeasible Deontic Conditionals and Conditional Goals Craig Boutilier

AAAI Conferences

We explore the notions of permission and obligation and their role in knowledge representation, especially as guides to action for planning systems. We first present a simple conditional deontic logic (or more accurately a preference logic) of the type common in the literature and demonstrate its equivalence to a number of modal and conditional systems for default reasoning. We show how the techniques of conditional default reasoning can be used to derive factual preferences from conditional preferences. We extend the system to account for the effect of beliefs on an agent's obligations, including beliefs held by default. This leads us to the notion of a conditional goal, goals toward which an agent should strive according to its belief state. We then extend the system (somewhat naively) to model the ability of an agent to perform actions. Even with this simple account, we are able to show that the deontic slogan "make the best of a bad situation" gives rise to several interpretations or strategies for determining goals (and actions). We show that an agent can improve its decisions and focus its goals by making observations, or increasing its knowledge of the world. Finally, we discuss how this model might be extended and used in the planning process, especially to represent planning under uncertainty in a qualitative manner.


Abstract Normative Systems: Semantics and Proof Theory

AAAI Conferences

In this paper we introduce an abstract theory of normative reasoning, whose central notion is the generation of obligations, permissions and institutional facts from conditional norms. We present various semantics and their proof systems. The theory can be used to classify and compare new candidates for standards of normative reasoning, and to explore more elaborate forms of normative reasoning than studied thus far.


Automated Reasoning in Normative Detachment Structures with Ideal Conditions

arXiv.org Artificial Intelligence

ARTICLE HISTORY Compiled October 24, 2018 ABSTRACT Systems of deontic logic suffer either from being too expressive and therefore hard to mechanize, or from being too simple to capture relevant aspects of normative reasoning. In this article we look for a suitable way in between: the automation of a simple logic of normative ideality and sub-ideality that is not affected by many deontic paradoxes and that is expressive enough to capture contrary-to-duty reasoning. We show that this logic is very useful to reason on normative scenarios from which one can extract a certain kind of argumentative structure, called a Normative Detachment Structure with Ideal Conditions. The theoretical analysis of the logic is accompanied by examples of automated reasoning on a concrete legal text. Keywords: Deontic Logic - Legal Reasoning - Normative Ideality 1. Introduction In the last decades, computer systems have played an important role in assisting people in a wide range of tasks, from searching over data to decision-making, and their use is required in an increasing number of fields. One of these fields is legal reasoning. New court cases and legislations are accumulated every day. In addition, international organizations like the European Union are constantly aiming at combining and integrating separate legal systems (Burley and Walter 1993).