L. T. McCarty. Defeasible deontic reasoning. In Proceedings of the Fourth International Workshop on Nonmonotonic Reasoning, Plymouth, Vt, 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....assumptions are given explicitly. However, for a full analysis of this paradox we also have to consider so called defeasibility interpretations of it, because the real problem of the Reykjavik paradox is how to interpret the sentences when more speci c obligations override more general ones [47,64]. Example 6 (Reykjavik Scenario, continued) NS 1 = hN; F I 1 ; i, NS 2 = hN; F I 2 ; i, N = f ( r) g) gjr) rjg)g, F I 1 = f: r) rjg) g, and F I 2 = f ( r) rjg)g. In NS 1 the obligation for ( r) is factually dependent on g, the obligation is overridden and ....

L.T. McCarty. Defeasible deontic reasoning. Fundamenta Informaticae, 21:125-148, 1994.

....to the present solution are faced. Notice that this paper addresses neither the problem of eliminating contradictions or dilemmas, nor the problem of reasoning about contradictory legal rules. These two problems come after it has been proved that a regulation is not consistent [7] 18] [12], 4] 16] 2] 2 Expressing regulations Let us note L, a first order language in which there is an unary function symbol denoted not, an unary predicate symbol denoted obligatory and there are two kinds of predicate symbols: the A predicate symbols and the P predicate symbols. The first ones ....

L.T. McCarty. Defeasible deontic reasoning. In Proceedings of the Fourth International Workshop on Non Monotonic Reasoning. Plymouth, 1992.

....see L. van der Torre. Y. Tan Contrary To Duty Reasoning with Preferences 19 example DP2. This solution seems like overkill. Moreover, it is unclear how to deal with the pragmatic oddity CP3. 4.1.3. Defeasibility Non monotonic techniques can be used to consistently formalize the paradox [54,44,47]. The problem of the paradox is that it is inconsistent, whereas intuitively it is consistent. Hence, a pragmatic formalization of the paradox can make use of restoring consistency techniques in case of a paradox. However, this solution is ad hoc. Restoring consistency is like treating symptoms ....

L.T. McCarty. Defeasible deontic reasoning. Fundamenta Informaticae, 21:125--148, 1994.

....possible to excuse themselves by claiming that their behavior was exceptional rather than criminal. 1 THE LOGIC OF NORMS Computer scientists use the logic of obligations, prohibitions and permissions called deontic logic since the early eighties to represent and reason with legal knowledge (McCarty, 1994), and recently it has been used to specify and analyze security issues about electronic networks (Conte and Falcone, 1997) to represent norms in qualitative decision theory (Pearl, 1993; Boutilier, 1994; Lang, 1996) and to represent rights, duties and commitments in multi agent systems (van der ....

McCarty, L. (1994). Defeasible deontic reasoning. Fundamenta Informaticae, 21:125--148.

....in exceptional circumstances. We will argue that this view on these systems, although understandable, is mistaken; it is not prima facie obligations that these logics represent. The second issue concerns a proposal of some to formalise timeless CTD structures using non monotonic techniques (e.g. (McCarty, 1994; Ryu and Lee, 1996) In these proposals, in circumstances where a primary obligation is violated, consistency is maintained by regarding the derivation of the primary obligation as somehow blocked by the derivation of the secondary obligation that comes into force. We here briefly summarise our ....

McCarty, L. T. (1994). Defeasible deontic reasoning. Fundamenta Informaticae 21:125--148.

.... typically formalize obligations that do not have weakening (of the consequent) Jen85] or defeasible conditionals, i.e. conditionals that do not have strengthening of the antecedent [Alc93] In a defeasible deontic logic it is argued that deontic detachment should sometimes hold and sometimes not [McC94, RL93, NY97] We say that deontic detachment holds as a defeasible rule [vdTT95, vdTT97b] The following example illustrates that the defeasibility in the Chisholm paradox is analogous to defeasibility in assumption based reasoning. Example 6 (Chisholm paradox, continued) Consider the two ....

L.T. McCarty. Defeasible deontic reasoning. Fundamenta Informaticae, 21:125-- 148, 1994.

....show that this distinction is essential for an adequate analysis of notorious paradoxes of deontic logic such as the Chisholm and Forrester Paradoxes . 1 Introduction In recent years defeasible deontic logic has become increasingly popular as a tool to model legal reasoning in expert systems [ McCarty, 1992; Meyer and Wieringa, 1994; Jones and Sergot, 1994 ] because defeasible reasoning is an important aspect of legal reasoning [ Prakken, 1993 ] Deontic logic is a modal logic in which the modal operator O is used to express that something is obligatory. 1 For example, if the proposition r ....

....O(h j r) which expresses that you ought to be helped (h) when you are robbed (r) If both O( r j ) and r are true, then we say that the obligation is violated by the fact r. In recent years it was argued by several authors that these dyadic obligations can be formalized in non monotonic logics [ McCarty, 1992; Horty, 1993; Ryu and Lee, 1994 ] In defeasible reasoning one can distinguish two types of defeasibility. To illustrate the difference between the two we consider the default rule :p p . This default can be defeated by the fact :p, or it can be overridden by another more specific default ....

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L.T. McCarty. Defeasible deontic reasoning. In Fourth International Workshop on Nonmonotonic Reasoning, Plymouth, 1992.

....une discussion. Avant toute chose, il faut remarquer que cet article ne traite ni le probl eme de l elimination des contradictions ou des dilemnes, ni le probl eme de raisonner avec des r eglementations incoh erentes. Ces deux probl emes viennent apr es celui de la d etection de l incoh erence. [10, 20, 15, 8, 6, 18, 5]. 2 Expression des r eglementa tions Notons L un langage du premier ordre qui a, entre autres, un symbole de pr edicat unaire not e obligatoire, un symbole de fonction unaire not e not et qui distingue, comme dans [1] deux types de pr edicats : les A pr edicats qui sont des pr edicats ....

L.T. McCarty. Defeasible deontic reasoning. In Proceedings of the Fouth International Workshop on Non Monotonic Reasoning. Plymouth, 1992.

....of Forrester (1984, p.196) His consistent formalization is based on rejection of the property weakening. 5 In his logic, fl:kflk is inconsistent whereas fl:k flg is consistent. 6 Defeasibility. Non monotonic techniques can be used to consistently formalize the paradox (Ryu Lee, 1993; McCarty, 1994; Nute Yu, 1997) The problem of the paradox is that it is inconsistent, whereas intuitively it is consistent. Hence, a pragmatic formalization of the paradox can make use of restoring consistency techniques in case of a paradox. 7 Non monotonic techniques were already used by Loewer and ....

....rule and 0 , and the deontic axiom ought implies can : fl ( jff) is accepted. and 0 : fl(ff1 j fi) F 1 ;p 1 ) fl(ff2 j fi) F 2 ;p 2 ) fl(ff1 ff 2 j fi) F 1 ThetaF 2 ;max(p 1 ;p 2 ) 16 This example has been discussed in the context of the Reykjavik Scenario (Belzer, 1986; McCarty, 1994; van der Torre, 1994; Makinson, 1998) in which S1 = ffl( rj ) fl( gj g) S2 = ffl( r :gj )g and r is read as telling the secret to Reagan and g as telling it to Gorbatchov. The example suggests that premises not only encode obligations but also independence (or irrelevance) assumptions. In S1 ....

McCarty, L. 1994. Defeasible deontic reasoning. Fundamenta Informaticae 21:125-- 148.

....and Levesque [16, 15, 17] They have proposed a logic that defines intentions in terms of goals and beliefs. Their proposal has generated some discussion and debate, some of which can be found in [18] 5.4 Obligation The notion of obligation has scarcely been studied in AI. See work by McCarty [45] and Boutilier [6] for early examples of work formalizing ought . Quite recently, Pearl has proposed a formalization of conditional obligations [51] 6 Final comments In this final section, we will briefly mention three aspects of agency which have not yet come up in this survey: perception, ....

L. T. McCarty. Defeasible deontic reasoning. In Fourth International Workshop on Nonmonotonic Reasoning, pages 139--147, 1992.

....for eating with your fingers and a 2 for washing your hands, because a 1 and :a 1 are contradictory. The traditional approach to these problematic CTD obligations is to weaken the notion of implication in such a way that the counterintuitive sentences are no longer derived. Horty [3] and McCarty [7], among others, have argued that the techniques of nonmonotonic logic may provide a better theoretical framework for deontic reasoning than the usual modal treatment. These nonmonotonic techniques are used to deal with some problematic aspects of CTD obligations in the Paradoxes . Horty focussed ....

....D 6 CF O( a 2 a 1 ) a case of defeasibility. When he tells both, he does not violate any obligations because a 1 and a 2 are considered as exceptions: the third sentence is an exception to the second sentence, and the fourth sentence is an exception to the first sentence. 8 McCarty [7] argues for a mixed defeasibility violability interpretation, which we will adopt here too. Mixed defeasibility violability interpretation. When X tells Reagan, it is identical to the defeasibility interpretation, i.e. a case of defeasibility. When X tells both, he should tell neither of them, D ....

L.T. McCarty, `Defeasible deontic reasoning', in Fourth International Workshopon Nonmonotonic Reasoning, Plymouth, (1992).

....given consistent readings; this investigation will be the main topic of the paper. Recently, it has been suggested that CTD reasoning is just an instance of defeasible reasoning, to which, accordingly, familiar techniques of nonmonotonic logics can be applied rather directly (e.g. Ryu Lee 91, McCarty 94] In section 4 we will argue that these proposals are mistaken, although understandable because of the ambiguity of many natural language examples. Instead we will follow suggestions of, among others, Jones Porn 85] that CTD structures can be represented consistently if a distinction is made ....

....problem was how to deal with conflicting primary and secondary obligations, while one of the virtues of nonmonotonic logics is that they are intended to cope with conflicting information. Indeed at least two suggestions along these lines have already appeared in the literature, Ryu Lee 91] and [McCarty 94] Let us look again at example 1: 1. There must be no fence. 2. If there is a fence, it must be a white fence. One plausible reading is that (1) has been formulated as a defeasible rule, understood to be subject to exceptions, and that (2) takes effect in these exceptional circumstances: there is ....

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L.T. McCarty. Defeasible deontic reasoning. Fundamenta Informaticae 21:125--148, 1994.

....example of being served asparagus. You should not eat with your fingers. But if you are served asparagus, then you should eat with your fingers. In the special case where you are served asparagus, the first obligation is less specific and hence cancelled by the second one. Various authors, e.g. [5, 8, 9], have investigated the formalization of defeasible conditional obligations (traditionally called prima facie obligations) deontic rules which are subject to exceptions. Explicit exceptions can be introduced in DIODE by formalizing a defeasible conditional obligation if a is the case then ....

L.T. McCarty. Defeasible deontic reasoning. In Fourth International Workshop on Nonmonotonic Reasoning, Plymouth, 1992.

....points of my suggestion and Horty s analysis are the same and although, moreover, both are based on Reiter s [24] default logic, there is an important difference. While the logic developed by Horty is in fact (like e.g. 12] a special defeasible logic for deontic reasoning, I suggest (like e.g. [15] and [17] to combine a deontic logic with an already existing general nonmonotonic formalism. The aim of this paper is to assess the merits of these two strategies of formalising defeasible deontic reasoning. I will compare the approaches in two stages. First I will carry out a case study, by ....

L.T. McCarty, Defeasible deontic reasoning. Fundamenta Informaticae 21 (1994), 125-148.

....j ) expresses that you ought not to be robbed , where stands for any tautology. If both fl( rj ) and r are true, then we say that the obligation is violated by the fact r. In recent years it was argued by several authors that these dyadic obligations can be formalized in non monotonic logics (McCarty, 1994; Horty, 1993; Ryu and Lee, 1993) In this article we argue that contrary to duty obligations do have a defeasible aspect, but a different one than is usually thought. The first part of torre.tex Date: December 31, 1996 Time: 10:41 THE MANY FACES OF DEFEAS I B I L I TY 81 this claim follows ....

....first one is called its primary obligation. CTD obligations refer to optimal sub ideal situations. In the sub ideal situation that fl(ff 1 j ) is violated by :ff 1 , the best thing to do is ff 2 . Recently, it was observed that this aspect of violations can be formalized in non monotonic logics (McCarty, 1994; Horty, 1993) theories of diagnosis (Tan and Van der Torre, 1994a; Tan and Van der Torre, 1994b) or qualitative decision theories (Boutilier, 1994) see also (Powers, 1967; Jennings, 1974; Pearl, 1993; Thomason and Horty, 1996) Since the late seventies, several temporal deontic logics and ....

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McCarty, L. T. (1994). Defeasible deontic reasoning. Fundamenta Informaticae 21:125--148.

....section 5 is devoted to a discussion. Notice that this paper addresses neither the problem of eliminating contradictions or dilemmas nor the problem of reasoning about contradictory legal rules. These two problems come after it has been proved that a regulation is not consistent [ 8 ] 9 ] 10 ] 11 ] 12 ] 13 ] 2 Expressing regulations Let us note L, a first order language such that, among other function symbols, there is a special unary function symbol denoted not and there are two kinds of predicate symbols: the A predicate symbols and the P predicate symbols. The ....

L.T. McCarty. Defeasible deontic reasoning. In Proceedings of the Fouth International Workshop on Non Monotonic Reasoning. Plymouth, 1992.

.... non monotonic consistency restoring techniques are insufficient to formalize contrary to duty reasoning (van der Torre Tan, 1995) 1997a) although the inconsistency of the two sets of obligations of the cottage housing regulations in Example 3 in SDL might suggest otherwise (Ryu Lee, 1993; McCarty, 1994; Yu, 1995) Consequently, Cdl should not be based on OD. It has to be based on factual defeasibility and it is therefore monotonic. 3 This paper is organized as follows. In Section 2 we introduce contextual obligations O fl (ffjfi) and O(ffjfi n fl) in a preference based logic and in Section 3 ....

McCarty, L. 1994. Defeasible deontic reasoning. Fundamenta Informaticae 21:125-- 148.

....nobody still addressed the precise problem of merging sets of norms as we defined it. But many works deal with the problem of reasoning with contradictory obligations, or more generally, contradictory norms. Their aim is then to define defeasible deontic reasoning (Ryu Lee, 1991, Horty, 1991, McCarty, 1992, Prakken, 1994, Van der Torre, 1994, Prakken Sergot, 1994) Most of these works consist in viewing norms as conditional norms which can be defeated via a nonmonotonic logic. Horty (Horty, 1991) introduces the notion of specificity, to defeat some rules. For instance, in the asparagus eater ....

McCarty, L. (1992). Defeasible Deontic Reasoning. In Proceedings of the Fourth International Workshop on Non Monotonic Reasoning, Plymouth.

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L. T. McCarty. Defeasible deontic reasoning. In Proceedings of the Fourth International Workshop on Nonmonotonic Reasoning, Plymouth, Vt, 1992.

No context found.

L.T. McCarty. Defeasible deontic reasoning. In Proceedings of the Fouth International Workshop on Non Monotonic Reasoning. Plymouth, 1992.

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L.T. McCarty. Defeasible deontic reasoning. Fundamenta Informaticae, 21:125-148, 1994.

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L.T. McCarty. Defeasible deontic reasoning. Fundamenta Informaticae 21:125--148 (1994).

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