Brewka, G.: Adding priorities and specificity to default logic. In: JELIA '94: Proceedings of the European Workshop on Logics in Artificial Intelligence, Springer-Verlag (1994) 247--260  Home/Search   Document Not in Database   Summary   Related Articles   Check

..... t n ) is false in s. In addition, miraculous disqualifications are assumed away, whenever possible, by applying defaults of the form ( a # action sequence) Since miraculous disqualifications are to be minimized with higher priority, we employ the concepts of Prioritized Default Logic [ Brewka, 1994 ] The report [ Thielscher, 1996 ] contains full details as well as a formal proof of the adequacy of this extension with regard to the theory developed in Section 3. As opposed to the formal language used in the preceding sections, our action calculus supports non propositional fluents, such ....

G. Brewka. Adding priorities and specificity to default logic. In C. MacNish, D. Pearce, and L. Pereira, eds., Proc. of the European Workshop on Logics in AI (JELIA), vol. 838 of LNAI, p. 50--65. Springer 1994.

....implies that the regular precondition Holds(Carries(o, p) s) in (1) does actually not hold. In this way, the high level controller uses its reasoning facilities to generate suitable explanations for the encountered failure [Martin and Thielscher, 2001] By appealing to prioritised default logic [Brewka, 1994] , one can specify qualitative knowledge of the relative likelihood of the various explanations for abnormal qualifications. The accompanying concept of preferred extensions then helps selecting the most likely explanation. In cases where it is impossible to provide an exhaustive specification of ....

G. Brewka. Adding priorities and specificity to default logic. In Proc. of the European Workshop on Logics in AI (JELIA-94), volume 838 of LNAI, pages 247-- 260. Springer, 1994.

....considered to be a problem, but are instead exploited as a useful feature that can provide an adequate formalization of the multi interpretability often present in real life information. In [14] this feature is expressed by adding as an extra parameter a selection function to a default theory. In [6] and [7] a similar approach is developed, based on priority orderings between defaults. In [8] the notion of belief set operator is introduced to formalize the multiple 21 outcomes of a non monotonic reasoning process, and a selection operator to make a choice between the different options. For ....

....and a selection operator to make a choice between the different options. For the application domain discussed here the latter approach is more suitable, because in this approach first all alternative interpretations are generated, and the selection is made afterwards. In the approaches of [14] [6], and [7] the reasoning process itself is controlled by the selection knowledge in such a manner that only one outcome is generated, and other options remain invisible. Such strategic knowledge is not yet available. However, in the future of this project such strategic knowledge may be acquired so ....

[Article contains additional citation context not shown here]

G. Brewka, "Adding Priorities and Specificity to Default Logic", in: C. MacNish, D. Pearce, L.M. Pereira (eds.), Logics in Artificial Intelligence, Proceedings of the JELIA-94, Lecture Notes in Artificial Intelligence, vol. 838, SpringerVerlag, 1994, pp. 247-260.

....particular, if at the current point in time one of the D is already entailed by the facts, only the second choice in the algorithm makes sense. In the case of default logic, one could use priorities between default rules or specificity of rules to restrict the number of possible choices (see [Br94]) The set of possible runs of our algorithm can be parametrized by selection functions. Such functions describe the choices which have to be made at each point in time (in a similar fashion as in [TT92] Then the good selection functions make use of heuristic knowledge to guide the reasoning ....

Brewka, G.: "Adding Priorities and Specificity to Default Logic", in: C. Intelligence, JELIA '94, Springer-Verlag, 1994, pp. 247-260. 13

....considered to be a problem, but are instead exploited as a useful feature that can provide an adequate formalisation of the multi interpretability often present in real life information. In [14] this feature is expressed by adding as an extra parameter a selection function to a default theory. In [6] and [7] a similar approach is developed, based on priority orderings between defaults. In [8] the notion of belief set operator is introduced to formalise the multiple outcomes of a non monotonic reasoning process, and a selection operator to make a choice between the different options. For the ....

....operator to make a choice between the different options. For the application domain discussed in this paper the latter approach is more suitable, because in this approach first all alternative interpretations are generated, and the selection is made afterwards. In the approaches of [14] [6], and [7] the reasoning process itself is controlled by the selection knowledge in such a manner that only one outcome is generated, and other options remain invisible. Such strategic knowledge is not yet available. However, in the future of this project such strategic knowledge may be acquired so ....

[Article contains additional citation context not shown here]

G. Brewka, "Adding Priorities and Specificity to Default Logic", in: C. MacNish, D. Pearce, L.M. Pereira (eds.), Logics in Artificial Intelligence, Proceedings of the JELIA-94, Lecture Notes in Artificial Intelligence, vol. 838, Springer-Verlag, 1994, pp. 247-260.

....rules suffice. More recently, Brewka published several papers that further elaborate on this idea by introducing default logics that only use normal default rules, and in which the specificity conflicts between default are handled by explicit priority orderings that are added to the logic (see [Br94a] and [Br94b] We want to generalize this perspective. Selection functions as introduced in [TT92] can be viewed as a generalization of Brewka s explicit priority orderings. The basic intuition is that instead of using justifications as techniques to control the specificity conflicts between ....

G. Brewka, Adding Priorities and Specificity to Default Logic, Proceedings of the JELIA-94, 1994.

....shown to be a useful tool for nature conservationists. After multiple interpretations of observation information have been identified, often a choice is made for one of them. Which view is (or which views are) most appropriate presumably requires additional heuristic (strategic) knowledge (cf. [3], 4] 12] One of the 16 areas of future research is to further analyze this choice process, in general terms, but also in particular for the knowledge based system. Future research will focus on the acquisition of this knowledge to be able to support users in the selection process. ....

G. Brewka, "Adding Priorities and Specificity to Default Logic", in: C. MacNish, D. Pearce, L.M. Pereira (eds.), Logics in Artificial Intelligence, Proceedings of the JELIA94, Lecture Notes in Artificial Intelligence, vol. 838, Springer-Verlag, 1994, pp. 247260.

....that is a strict partial order. The static concept of preference corresponds to most previous approaches to preference handling in logic programming and nonmonotonic reasoning, where the preference information is specified as a fixed relation at the meta level (cf. Baader and Hollunder, 1993; Brewka, 1994; Zhang and Foo, 1997; Brewka and Eiter, 1999; Wang et al. 2000] The idea behind our methodology for compiling preferences is straightforward. Given a preference handling strategy , our approach provides a mapping T that transforms an ordered logic program into a standard logic program T ....

.... information of some form (see, e.g. Gelfond et al. 1989; Konolige, 1988; Rintanen, 1994; Nebel, 1998; Eiter and Gottlob, 1995; Brewka, 1989; Brewka, 1996] Prioritised versions of default logic and logic programming 33 under the answer set semantics includes [Baader and Hollunder, 1993; Brewka, 1994; Rintanen, 1998b; Sakama and Inoue, 1996; Gelfond and Son, 1997; Zhang and Foo, 1997] as well as those approaches discussed earlier. As argued in [Delgrande and Schaub, 2000a] these approaches can be divided into descriptive and prescriptive approaches. In the former case, one has a wish list ....

[Article contains additional citation context not shown here]

G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, editors, European Workshop on Logics in Artificial Intelligence (JELIA'94), Lecture Notes in Artificial Intelligence, pages 247--260. Springer-Verlag, 1994.

....2 INFSYS RR 1843 02 01 1 Introduction Handling preference information plays an important role in applications of knowledge representation and reasoning. In the context of logic programs and related formalisms, numerous approaches for adding preference information have been proposed, including [1, 4, 5, 8, 11, 12, 18, 22, 24, 25, 27, 29] to mention some of them. These approaches have been designed for purposes such as capturing specificity or normative preference; see e.g. 7, 11, 25] for reviews and comparisons. The following example is a classical situation for the use of preference information. Example 1 (bird penguin) ....

....of an answer set and is more efficient in general. Note that, by suitable adaptions of the meta programs, other ASP engines such as Smodels [23] can be used as well. INFSYS RR 1843 02 01 3 B preferred answer set semantics refines previous approaches for adding preferences to default rules in [4, 5]. It is defined for answer sets of extended logic programs [17] and is generalized to Reiter s default logic in [6] An important aspect of this approach is that the definition of preferred answer sets was guided by two general principles which, as argued, a preference semantics should satisfy. As ....

[Article contains additional citation context not shown here]

G. Brewka. Adding Priorities and Specificity to Default Logic. In Proceedings JELIA '94, LNAI 838, pages 247--260. Springer, 1994.

....in human s commonsense reasoning. In fact, the famous example of whether penguins fly because they are birds [23] in default reasoning is an example of reasoning with specificity. Reasoning with specificity also constitutes a difficult problem which has been studied extensively in the literature [1, 5, 7, 14, 16, 29, 31, 38]. Formally a default theory T could be defined as a pair (E; K) where E is a set of evidence or facts representing what we call the concrete context of T , and K = D; B) constitutes the domain knowledge consisting of a set of default rules D and a first order theory B representing the background ....

....T could be defined as a pair (E; K) where E is a set of evidence or facts representing what we call the concrete context of T , and K = D; B) constitutes the domain knowledge consisting of a set of default rules D and a first order theory B representing the background knowledge. In the literature [1, 5, 7, 14, 16, 29] the principle of reasoning with specificity is enforced by first determining a set of priority orders between defaults in D using the information given by the domain knowledge K. Based on these priorities between defaults and following some sensible and intuitive criteria, the semantics of T is ....

[Article contains additional citation context not shown here]

Brewka, G.: Adding Priorities and Specificity to Default Logic, Proc. JELIA 94, LNAI 838, Springer Verlag, 247--260.

....to the approach in [Sakama and Inoue, 1996] where preferences on literals are investigated. While the approach of [Gelfond and Son, 1997] remains within NP, it advocates strategies that are non selective. Approaches that can be addressed within this framework include [Baader and Hollunder, 1993; Brewka, 1994] that were originally proposed for default logic. 2 Definitions and notation We assume a basic familiarity with logic programming under answer set semantics [Gelfond and Lifschitz, 1991] An extended logic program is a finite set of rules of the form L 0 L 1 ; Lm ; not Lm 1 ; ....

....body body (r) is eliminated there is no way to detect whether head (r 0 ) 2 body (r) holds in case of r r 0 . Such an approach is pursued in [Wang et al. 2000] for characterizing preferred answer sets. Following earlier approaches based on default logic [Baader and Hollunder, 1993; Brewka, 1994] this approach is based on the concept of activeness: Let X;Y Lit be two sets of literals in an ordered logic program ( A rule r in is active wrt the pair (X; Y ) if body (r) X and body (r) Y = Definition 1 (Wang et al. 2000) Let ( be an ordered logic program and let ....

G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, eds, Proc. JELIA'94, p 247--260. Springer, 1994.

....of (11) with either x Movable(A) or x Functioning(Gripper of ( Robbie) As will be shown in Section 3.5 below, this approach can also be used to account for so called weak qualifications, that is, unexpected e#ects of actions. Furthermore, by appealing to prioritized default logic [1], one can specify qualitative knowledge of the relative likelihood of the various explanations for abnormal qualifications (cf. Section 3.4 below) The accompanying concept of preferred extensions helps selecting the most reasonable explanations in case of unexpected action. 3 Addressing the ....

....action. Otherwise, the empty list is returned. 3. 4 Selection of the Preferred Extension Extensions are constructed in accordance with the underlying set prioritized default logic, which is an extension of the prioritized default logic and can be used to define preferences between defaults [1, 21]. The preference relations in the program are defined with or without context dependency. The first case defines a set preference ordering among defaults so that any two instances of a default concerning the same object are compared to an instance of another default concerning the object. If there ....

Gerhard Brewka. Adding priorities and specificity to default logic. In C. MacNish, D. Pearce, and L. M. Pereira, editors, Proc. of the European Workshop on Logics in AI (JELIA), volume 838 of LNAI, pages 247--260, York, UK, September 1994. Springer.

.... [12] hierarchic autoepistemic logic [15] prioritized theory revision [2, 19] prioritized logic programming [25, 28] or prioritized abduction [10] Also several prioritized versions of Reiter s default logic, the logic we are dealing with in this paper, have been described in the literature [16, 4, 1, 9], as well as of defeasible logics beyond default logic [20, 13] However, as we will show in Section 3, these approaches are not fully satisfactory. It turns out that some of them implicitly recast Reiter s default logic to a logic of graded beliefs, while others do overly enforce the application ....

....of this paper, we will restrict our discussion to fully prioritized default theories. Unless stated otherwise, all default theories are tacitly assumed to be closed. 3 Problems with Existing Approaches Different prioritized versions of default logic have been proposed in the literature, e.g. [16, 4, 1, 24, 9]. We will show that all of them fail to satisfy natural principles for preference handling in default logic. 3.1 Principles for priorities The first principle can be viewed as a meaning postulate for the term preference and states what we consider a minimal requirement for preference handling ....

[Article contains additional citation context not shown here]

G. Brewka. Adding Priorities and Specificity to Default Logic. Proc. JELIA '94, LNAI 838, pp. 247--260, 1994.

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Brewka, G. (1994a). Adding Priorities and Specificity to Default Logic. In Proceedings JELIA '94, LNAI 838, pages 247--260. Springer.

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Brewka, G.: Adding priorities and specificity to default logic. In: JELIA '94: Proceedings of the European Workshop on Logics in Artificial Intelligence, Springer-Verlag (1994) 247--260

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Brewka, G. 1994. Adding priorities and specificity to default logic. In Pereira, L., and Pearce, D., eds., European Workshop on Logics in Artificial Intelligence (JELIA'94), Lecture Notes in Artificial Intelligence, 247-- 260. Springer Verlag.

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G. Brewka. Adding priorities and specificity to default logic. In Logics in Artificial Intelligence, European Workshop, JELIA '94, pages 247-- 260, York, UK, 1994.

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Brewka, G.: Adding priorities and specificity to default logic, Proceedings of the European Workshop on Logics in AI (JELIA-94), 838, Springer, 1994.

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G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, editors, European Workshop on Logics in Artificial Intelligence (JELIA'94), Lecture Notes in Artificial Intelligence, pages 247--260. Springer-Verlag, 1994.

No context found.

G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, editors, European Workshop on Logics in Artificial Intelligence (JELIA'94), Lecture Notes in Artificial Intelligence, pages 247--260. Springer Verlag, 1994.

No context found.

G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, editors, European Workshop on Logics in Artificial Intelligence (JELIA'94), Lecture Notes in Artificial Intelligence, pages 247--260. Springer Verlag, 1994.

No context found.

G. Brewka, `Adding priorities and specificity to default logic', in Proc. JELIA, eds., L. Pereira and D. Pearce, pp. 247--260. Springer, (1994).

No context found.

G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, editors, European Workshop on Logics in Artificial Intelligence (JELIA'94), Lecture Notes in Artificial Intelligence, pages 247--260. Springer Verlag, 1994.

No context found.

G. Brewka. Adding priorities and specificity to default logic. In L. Pereira and D. Pearce, eds, Proc. JELIA'94, p 247--260. Springer, 1994.

No context found.

G. Brewka. Adding priorities and specificity to default logic. In Proc. of the European Workshop on Logics in AI (JELIA-94), volume 838 of LNAI, pages 247--260. Springer, 1994.

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