P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Moshe Y. Vardi, editor, Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, pages 83--95. Morgan Kaufmann, 1988. Pacific Grove, California.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....which is the ideal case. An example better illustrates problem (2) in order to present the case for a library. As an example, consider a set of formulas, partitioned according to a total order relation over each formula s entrenchment level. Entrenchment levels were originally proposed in [Grdenfors and Makinson 1988] to denote the willingness to give up a belief, here represented by a formula. Two formulas belong to the same partition i they have the same entrenchment level. Using the notation from [Dixon 1994] we represent entrenchment levels by positive integers (proportional to their intended ....

Grdenfors P., Makinson D. Revisions of Knowledge Systems using Epistemic Entrenchment. Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, 83-95.

.... of rationality postulates for belief contractions and belief revisions, based on the idea of minimal change, are given and two different tools, partial meet model and epistemic entrenchment ordering, for constructing belief change opera tions have been developed in [Alchourrdn et al. 1985] and [G denfors and Makinson 1988 ] respectively. Al though AGM s belief change operators appear to capture of what is required of an ideal system of belief change, they are not suitable to characterize changes of beliefs with sets of new beliefs, especially with infinite sets. A number of studies on extending and generalizing ....

P. Ghrdenfors and D. Makinson, Revisions of knowledge systems using epistemic entrenchment, in: M. Vardi, ed., Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, edited by M. Vardi (Morgan Kaufmann Publ., Los Altos, CA, 1988) 83-95.

....If A had not occurred, then B would have occurred. Hirst cites these problems as an argument against an intensional treatment. Second, we can make counterfactual claims about the prevented event, e.g. the strike would have been long. The intuition guiding our treatment is the standard one, e.g. [7]: that although negotiations prevented a strike in the actual context world, there is some minimally different context world where the negotiations didn t occur (or failed) and the strike went ahead. Recall that our KR contexts are defined by axioms that at least (a) restrict the possible ....

Gardenfors, P. and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. Proceedings 2nd Conference on Theoretical Aspects of Reasoning About Knowledge, 83--95, Morgan Kaufmann, San Francisco, 1988.

....work and concludes. 2 REPRESENTING RELIABILITY RELATIONS In this section we introduce the formalism used in this paper. One of the distinguishing features of our approach is the ablility to reason about the reliability of the available information in the logical language. In the AGM approach [7, 8] entrenchment relations are used to represent how strongly an agent sticks to his beliefs: the more entrenched a formula, the less willing to give it up the agent is. Entrenchment relations have several properties which are based on the logical strength of the formulas. For instance, logically ....

Gardenfors, P., Makinson, D., Revisions of Knowledge Systems Using Epistemic Entrenchment. In: Vardi, M. (ed): Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, Morgan Kaufmann, Los Altos, 1988

.... The formula whose inference from the base is to 1 be determined imposes a prioritization on the formulas in the base (thus reorganizing the temporal ordering present in the base) Therefore, we do not treat a belief base as a set but rather as a linear order much like an entrenchment (see [GM88], Geo97] Since we take relevance into account we cannot use an entrenchment ordering in our method. This procedure for inference serves as a generalization of the method presented in [Geo96] and [CP99] In this way, we hope to present a model for belief revision that is a plausible ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, pages 661--672, 1988.

....a sentence into a belief set such that certain postulates are satisfied. These postulates provide rationality criteria bounding the properties of any revision function. There have been various modellings of these postulates, including that of the epistemic entrenchment of sentences in a language [ GM88 ] In this paper we will be most concerned with a modelling of revision, due to Adam Grove [ Gro88 ] that is based on Lewis system of spheres semantics for counterfactuals [ Lew73 ] In this paper I am concerned with fundamental notions of belief revision. The question addressed is a ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Proc. Second Theoretical Aspects of Reasoning About Knowledge Conference, pages 83--95, Monterey, Ca., 1988.

....would give up more beliefs than necessary. A conservative revision might instead retain one of P or Q as beliefs. Conservatism is an important element of philosophical theories of belief revision and the related topic of counterfactuals (see (Quine and Ullian, 1978; Harman, 1986; Stalnaker, 1984; Gardenfors, 1988)) and also appears as one of the central functions of a reason maintenance system (RMS, n ee truth maintenance system) Doyle, 1979; Doyle, 1983b; Doyle, 1983a) Habits may be viewed as implicitly rational procedures for making certain limited decisions. For example, a field soldier s habit of ....

....choosing assumptions is closely related to the more general problem of rationally updating or revising beliefs as new information is gained. The usual approach, as mentioned earlier, is to make belief revisions conservative, minimizing the changes made in the set of beliefs (Harman, 1986; Gardenfors, 1988). There is no logical justification for conservatism as a principle of belief revision. For example, the frame problem is a problem precisely because logic alone says nothing about persistence of belief. Indeed, the mere truth of some belief is no reason for holding it in memory, for otherwise ....

[Article contains additional citation context not shown here]

Gardenfors, P. and Makinson, D. 1988. Revisions of knowledge systems using epistemic entrenchment. In Vardi, M. Y., editor, Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, pp. 83--95.

....and [Hajek et al. 1994] such a notion of comparative possibility can be cast into modal logic and is equivalent to that underlying Lewis [1986] logic of conditionals. The dual necessity orderings lie at the core of the AGM theory of belief revision (under the name epistemic entrenchment [G ardenfors, 1988] , or expectation orderings [G ardenfors and Makinson, 1994] as well as of theories of nonmonotonic reasoning that exploit a partial or complete ordering of interpretations of a language (such as that of Shoham [1988] Kraus et al. 1990] Goldszmidt and Pearl [1992] Lehmann and Magidor ....

.... forms of QI3 QI4 especially do not hold for ; 7 QUALITATIVE INDEPENDENCE AND BELIEF CHANGE Several notions of independence and relevance studied above, among which qualitative independence, can be fully expressed in the framework of revision of propositional theories also called belief sets [G ardenfors, 1988] . Revising a belief set K by a sentence A means to add A to K and to restore consistency so as to keep A. Gardenfors [1990] proposes the following criterion for the revision of a belief set: If a belief state K is revised by a sentence A, then all sentences in K that are independent of the ....

[Article contains additional citation context not shown here]

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Proc. of the 2nd Conf. on Theoretical Aspects of Reasoning About Knowledge, M.Y. Vardi, ed. pp. 83--95. Morgan Kaufmann, Los Altos, CA, 1988.

....that imply this belief from the belief set i.e. ff 2 K; ff = 2 K Gamma ff ; Revision (K ff ) is the acceptance of a belief that may contradict existing beliefs in the belief set i.e. ff = 2 K; ff 2 K; ff 2 K ff . One of the constructions of these functions is by epistemic entrenchment (6) [10]. It is a total pre ordering of beliefs with respect to their significance from the point of view of an agent. When applying changes to the agent s belief set K, beliefs with the lowest degree of epistemic entrenchment are given up first. This reflects the intuition of minimal changes because an ....

....engineering process. By applying belief revision to the agent s memory, some domain knowledge may be contracted from the memory over time. Therefore, domain knowledge perhaps needs to be transferred to the agent s memory periodically in accordance with the postulates of epistemic entrenchment [10]. However, exactly how this can be done requires further investigation. The current framework proposes that when a product is required or rejected by the consumer, the corresponding belief will be induced based on Eq. 1) and be revised to the agent s memory by maxi adjustment. Therefore, the ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Moshe Y. Vardi, editor, Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, pages 83--95, San Francisco, CA, 1988. Morgan Kaufmann Inc.

....epistemic states are not belief sets may be found in [BLS99] 4 This work provides a semantics for theory revision a la AGM, or for a sub family of such revisions. It is the first such effort to describe semantically the whole revision operation in a unified way. Previous attempts [Gro88] [GM88] describe the revision of each theory K by a different structure without any glue relating the different structures: sphere systems or epistemic entrenchment relations, corresponding to different K s. In this paper, the revisions of the different K s are obtained from the same pseudo distance. A ....

P. Gardenfors and D. Makinson, "Revisions of Knowledge Systems using Epistemic Entrenchment", in Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, M.Y.Vardi ed., pp. 83-95, Morgan Kaufmann, Monterey, California, 1988.

....an entrenchment ordering 2 As is well known, a relation is reflexive, Euclidean and transitive if and only if it is an equivalence relation (i.e. reflexive, symmetric and transitive) Thus, M ert K consists of these structures where the K i s are equivalence relations. 6 over formulas [GM88] This ordering dictates how the agent s beliefs change. For example, in [Gro88] the new beliefs are characterized by the most preferred worlds that are consistent with the new observation, while in [GM88] beliefs are discarded according to their degree of entrenchment until it is consistent to ....

....of these structures where the K i s are equivalence relations. 6 over formulas [GM88] This ordering dictates how the agent s beliefs change. For example, in [Gro88] the new beliefs are characterized by the most preferred worlds that are consistent with the new observation, while in [GM88] beliefs are discarded according to their degree of entrenchment until it is consistent to add the new observation to the resulting set of beliefs. Keeping this insight in mind, we now describe plausibility measures [FH95,FH97b] This is a notion for handling uncertainty that generalizes previous ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Proc. Second Conference on Theoretical Aspects of Reasoning about Knowledge, pages 83--95. Morgan Kaufmann, San Francisco, Calif., 1988.

....with x, is (possibly only vacuously) retracted from K. The primary function of is in fact to identify this intermediate belief set K Gamma :x as determined by the following constructive definition: ffl (C) b 2 K Gamma a iff b 2 K and either a OE (a b) or a Gardenfors and Makinson [11] have shown that if satisfies the constraints (SEE1) SEE5) then the ensuing revision operation (constructed from by (C) and the 4 Levi Identity) satisfies all the Gardenfors postulates of belief revision. Furthermore, it has also been shown that from every well behaved belief revision ....

Gardenfors, Peter and David Makinson, "Revision of Knowledge Systems using Epistemic Entrenchment," in Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, M. Vardi ed., Los Altos, CA: Morgan Kaufmann. pp. 83-95, 1988.

....Plausibility Measures Most non probabilistic approaches to belief change require (explicitly or implicitly) that the agent has some ordering over possible alternatives. For example, the agent might have a preference ordering over possible worlds [5,32,39] or an entrenchment ordering over formulas [28]. This ordering dictates how the agent s beliefs change. For example, in [32] the new beliefs are characterized by the most preferred worlds that are consistent with the new observation, while in [28] beliefs are discarded according to their degree of entrenchment until it is consistent to add ....

....a preference ordering over possible worlds [5,32,39] or an entrenchment ordering over formulas [28] This ordering dictates how the agent s beliefs change. For example, in [32] the new beliefs are characterized by the most preferred worlds that are consistent with the new observation, while in [28] beliefs are discarded according to their degree of entrenchment until it is consistent to add the new observation to the resulting set of beliefs. Keeping this insight in mind, we now describe plausibility measures [20,24] This is a notion for handling uncertainty that generalizes previous ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In M. Vardi, editor, Proc. Second Conference on Theoretical Aspects of Reasoning about Knowledge, pages 83--95. Morgan Kaufmann, San Francisco, 1988. 61

.... Belief Revision Paradigm The AGM framework [1] formalises consistent and minimal belief changes by sets of postulates and belief functions e.g. expansion (K ff ) contraction (K Gamma ff ) and revision (K ff ) One of the constructions of these functions is by epistemic entrenchment (6) [9]. Beliefs with the lowest degree of epistemic entrenchment are given up when inconsistency arises because of applying changes. Nevertheless, for computer based implementation, finite partial entrenchment ranking (B) which ranks a finite subset of beliefs with the minimum possible degree of ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Moshe Y. Vardi, editor, Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, pages 83--95, San Francisco, CA, 1988. Morgan Kaufmann Inc.

....then we obtain the theory we started with. Intuitively then, this postulate forces a minimal amount of information to be lost during a contraction. The postulates for contraction identify a class of functions for a knowledge base and for each one of these functions Gardenfors and Makinson [8] showed that there is a preference criterion that can be used to construct it. The most controversial of the contraction postulates is recovery, Gamma 5) because one can argue that it is not always an appropriate requirement, especially for a limited reasoning agent. A withdrawal function ....

....provides the theoretical basis for the one we adopt. Theorem 6. An epistemic entrenchment ordering is finitely representable if and only if it has a finite number of natural partitions, and for all 2 L, cut ( is finitely axiomatizable. The following result of Gardenfors and Makinson [8] provides us with a constructive method for building change functions from an epistemic entrenchment ordering. Theorem 7 gives a condition that can be used for constructing a contraction function, and Theorem 8 provides a similar one for constructing a revision function. Theorem 7. Let T be a ....

[Article contains additional citation context not shown here]

P. Gardenfors and D. Makinson. Revisions of Knowledge Systems using Epistemic Entrenchment. In the Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, 83 -- 96, 1988.

.... hand, those that are based on simple belief sets or on possible worlds have underlying structures that are too homogeneous to distinguish between inferences that are felicitous to cancel and inferences that are not; while on the other hand, those that put more structure on the belief sets, such as Gardenfors and Makinson s (1988), experience the same problems as the multivalued based theories that we have discussed in the previous paragraph. In this paper, we argue that a possible way to account for both these facets of cancelability is to use the multiple definition of satisfaction that was provided by Marcu and Hirst ....

Gardenfors, P., and Makinson, D. 1988. Revision of knowledge systems using epistemic entrenchment. In Vardi, M., ed., Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, 83--95. Los Altos, CA: Morgan Kaufmann.

....between Mod( and interpretations, i.e. I 0 I means that I 0 is closer to Mod( than I. Then, Min(M; can be seen as the set of all the closest interpretations in M to Mod( Gardenfors and other researchers established a set of postulates that revision operators must satisfy [1, 11]. Their work was located in the framework of knowledge sets or deductively closed set of formulae. Katsuno and Mendelzon formulated an equivalent set of postulates in the framework of knowledge bases [12] It has been proved that any proposed revision operator which satisfies the above mentioned ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, pages 83--95, 1988.

....and analyze specific revision schemes that generate revision operations by employing some preference information. One such revision scheme is, for instance, the partial meet revision scheme [1] Another scheme uses so called epistemic entrenchment orderings in order to generate revision operations [12]. If one wants to apply this theory in a computer science or artificial intelligence application, there are two severe problems. First of all, the assumption that belief states are modelled by deductively closed sets of sentences seems to be com 1 DFKI, Stuhlsatzenhausweg 3, 66123 Saarbrucken, ....

....ordering is a complete preorder over L. The strict part of this preorder will be denoted by OE in the following. Using such a relation, one can define a revision scheme, which we will call cut revision: K : OE def = f 2 K j :OE OE g OE: 4) From results by Gardenfors and Makinson [12] and Rott [23] it follows that class of belief revision operations generated by this scheme coincides with the class of revision operations satisfying all rationality postulates. 3 PRIORITIZED MEET BASE REVISION Although the theory sketched above provides us with a good picture of the ways a ....

P. Gardenfors and D. Makinson, `Revision of knowledge systems using epistemic entrenchment', in Proc. TARK-88, Asilomar, CA, (1988).

....our translation, is in bijective correspondence with the Gardenfors Makinson expectation inference relations. This is how the first representation result for rational inference is obtained. This result adds to a long tradition of defining nonmonotonic logics with orderings of formulas ( 4] 20] [7], 21] The above representation result is more constructive than the semantical completeness of preferential models. However, rational orderings must have a concise, constructive representation. To this end, we encode a natural way of applying defaults into a new class of consequence ....

....ordering satisfies 1. connectivity, i.e. ff fi or fi ff, and 2. either ff fi, for all fi 2 L, or :ff fi, for all fi 2 L. We should mention that the above properties of rational relations are not new. It is not easy to assign credits, but they have appeared in works in belief revision ([7]) possibilistic logic ( 3] 4] fuzzy logic ( 28] theory of evidence ( 24] and economics ( 23] see [8] for a historical reference) Gardenfors and Makinson define the following maps between the class of expectation inference relations and rational orderings. Definition 3.2. 8] Given a ....

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, pages 661--672, 1992.

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Grdenfors, P. and D. Makinson. (1988): "Revisions of knowledge systems using epistemic entrenchment", in Proceedings of the Second Conference on Theoretical Aspects of Reasoning about Knowledge, M. Vardi ed. (Los Altos, CA: Morgan Kaufmann).

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P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In Moshe Y. Vardi, editor, Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, pages 83--95. Morgan Kaufmann, 1988. Pacific Grove, California.

No context found.

Gardenfors, P. & Makinson, D. (1988) Revisions of Knowledge Systems Using Epistemic Entrenchment, Proceedings of the Second Conference on Theoretical Aspects of Reasoning About Knowledge, pp. 83-95.

No context found.

P. Gardenfors and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. In TARK'88, pages 83--96, 1988.

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Gardenfors, P. and D. Makinson. Revisions of knowledge systems using epistemic entrenchment. Proceedings 2nd Conference on Theoretical Aspects of Reasoning About Knowledge, 83--95, Morgan Kaufmann, San Francisco, 1988.

No context found.

P. Gardenfors and D. Makinson. Revisions of Knowledge Systems Using Epistemic Entrenchement. In M. Vardi, editor, Proc. 2nd TARK, pages 83--95. Morgan Kaufmann, Los Altos CA, 1988.

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