M. Winslett. Sometimes updates are circumscription. In N. S. Sridharan, editor, Proceedings of the Eleventh International Joint Conference on Artificial Intelligence (IJCAI '89), pages 859--863, Detroit, Michigan, 1989. Morgan Kaufmann.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....For instance, Ginsberg s operator and CIRC have the same time complexity and the same compactability properties (see [2, 9, 6] for the results on CIRC) It is therefore natural to ask whether this is a chance or not. A rst study of relationships between belief revision and CIRC has been done in [23] where the author remarked similarities between CIRC and her operator. Subsequently, in [14] the authors pointed out interesting connections between CIRC and several belief revision operators, thus extending the result of [23] In particular, they proved that CIRC can be compactly represented by ....

....study of relationships between belief revision and CIRC has been done in [23] where the author remarked similarities between CIRC and her operator. Subsequently, in [14] the authors pointed out interesting connections between CIRC and several belief revision operators, thus extending the result of [23]. In particular, they proved that CIRC can be compactly represented by means of several belief revision operators, i.e. given a propositional formula F , two formulas T and P , of size polynomial w.r.t. jF j, exist such that T ffi P is logically equivalent to CIRC(F ) As remarked in [14] this ....

M. Winslett. Sometimes updates are circumscription. In Proc. of IJCAI-89, pages 859863, 1989.

....defined by Nebel in [Neb91] Here we do not analyze his definitions. WIDTIO. Since there may be exponentially many new theories in T # G P , a simpler (but somewhat drastical) approach is the so called WIDTIO (When In Doubt Throw It Out) which is defined as T # W id P . #W (T, P ) # P [Win89]. Note that formula based approaches are sensitive to the syntactic form of the theory. That is, the revision with the same formula P of two logically equivalent theories T 1 and T 2 , may yield di#erent results, depending on the syntactic form of T 1 and T 2 . We illustrate this fact through an ....

..... The underlying idea is that the original knowledge base T was completely inaccurate w.r.t. everything mentioned in P . Hegner. Let# be the variables of P . The models of Hegner s revised theory are defined as M(T #H P ) N # M(P ) #M # M(T ) N#M ## . For further details see [Win89]. Weber s revision is slightly less drastic. It assumes that the letters whose interpretation was wrong are a subset of the letters of P , i.e. only those occurring in a minimal di#erence between models of T and P . Weber. Same definition as Hegner s update, but# . ##(T, P ) 5 3 ....

M. Winslett. Sometimes updates are circumscription. In Proceedings of the Eleventh International Joint Conference on Artificial Intelligence (IJCAI'89), pages 859--863, 1989.

.... formalize persistency by stating special default rules ( 9] In logic programming, various versions of negation as failure have been defined to specify that fluents persist if other fluents can not be proved to hold (see [3,6,8] In this paper we generalize a particular approach introduced in [14,15] and [4] The overall framework is propositional logic with respect to an underlying signature L. We denote by Mod L the set of all propositional models with respect to L. In this paper, however, we do not make use of the fact that Mod L is induced by L. We abstract from this and view ....

....by definition, # is minimal with respect to #, i.e. there is no other explanation # # #= # with # # # # . In [13,1] the authors state general representation results for preference relations between arbitrary sequences of models. A more intuitive approach to exclude such examples is due to [14,15]. The idea is to assume the notion of a distance between arbitrary worlds. Definition 5 (Distance dist dist dist) A distance dist is a function that associates to any two worlds a nonnegative rational number: dist : W W # I Q; A 1 , A 2 ) ## dist(A 1 , A 2 ) The idea of [14,15] was to ....

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Marianne Winslett. Sometimes updates are circumscription. In Proc. 11th Int. Joint Conf. on Artificial Intelligence (IJCAI'89), pages 859--863, 1989.

.... formalize persistency by stating special default rules ( 9] In logic programming, various versions of negation as failure have been de ned to specify that uents persist if other uents can not be proved to hold (see [3,6,8] In this paper we generalize a particular approach introduced in [15,16] and [4] The overall framework is propositional logic with respect to an underlying signature L. We denote by Mod L the set of all propositional models with respect to L. In this paper, however, we do not make use of the fact that Mod L is induced by L. We abstract from this and view this set ....

....if by de nition, is minimal with respect to , i.e. there is no other explanation 0 6= with 0 . In [13,1] the authors state general representation results for preference relations between arbitrary sequences of models. A more intuitive approach to exclude such examples is due to [15,16]. The idea is to assume the notion of a distance between arbitrary worlds. Daniel will, dass wir hier From Dix to Karl: die Dreiecksungleichung diskutieren. Kannst Du mir einen Input geben ) De nition 5 (Distance dist dist dist) A distance dist is a function that associates to any two worlds a ....

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Marianne Winslett. Sometimes updates are circumscription. In Proc. 11th Int. Joint Conf. on Articial Intelligence (IJCAI'89), pages 859-863, 1989.

....update. Applying for example [2] to the turkey scenario leads to non intuitive results, as we show in section 2. In this paper, we propose a model driven semantics for an update operation capable of taking into account an explicit transition model. It extends the model driven semantics defined in [10] for the Possible Model Approach by allowing an explicit expression of persistence. The transition model provides a more powerful and flexible way to represent how the world tends to change along time. It can moreover be stressed that non only persistence information but also default and ....

....and we point out the flaws of our [2] proposal. The transition model is presented in section 3. The semantics of the update operation is defined in section 4 and illustrated by examples in section 5. The relation between PMA and preferential models (and circumscription) has been highlighted by [10] s and [8] s. We show in section 6 that it can be extended to take into account an explicit transition model and how preferential models can then capture the semantics we defined. In the last section, we conclude by comparing our approach to the related ones more precisely. 2 A Motivating ....

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Marianne Winslett. Sometimes updates are circumscription. In Proceedings of the IJCAI Conference, pages 859--863, Detroit, 1989. PI n884

.... In most cases, the analysis is about the possibility of translating formulae from di#erent formalisms to Propositional Logic (PL) For example, Ben Eliyahu and Dechter (1991, 1994) proposed a translation from default logic to PL, and a translation from disjunctive logic programs to PL, while Winslett (1989) introduced a translation from revised knowledge bases to PL, and Gelfond, Przymusinska, and Przymusinskyi (1989) defined a translation from circumscription to PL. All the above translations, as well as many other ones in the literature, lead to an exponential increase of the size of the formula, ....

....a knowledge base KB is translated into another knowledge base f(KB) which can 12 Space Efficiency of Propositional Knowledge Representation Formalisms be used to represent the same set of theorems. More precisely, we have that each theorem # of KB is represented by a theorem g KB (#) of f(KB) Winslett (1989) has shown an example of a reduction from updated knowledge bases to PL that is theorem preserving but not model preserving. Using Winslett s reduction, one could use the same machinery for propositional reasoning in the KB, both before and after the update (plus the reduction) Also the reduction ....

Winslett, M. (1989). Sometimes updates are circumscription. In Proceedings of the Eleventh International Joint Conference on Artificial Intelligence (IJCAI'89), pp. 859--863.

....formalisms are translatable one into another, although such translation may lead to an exponential increase of the size of the formula. Most of the translations have Propositional Logic (PL) as their target formalism. e.g. BED91] from default logic to PL, from disjunctive logic programs to PL, [Win89] from revised knowledge bases to PL, from circumscription to PL. Only very recently researchers started analyzing the space eciency of PKR formalisms; this kind of investigation includes questions such as is exponential increase of the above mentioned translations intrinsic, or is it possible to ....

.... knowledge base KB in F 1 there exists a poly time function g KB such that for every query Q on the variables of KB it holds that KB F1 Q i f(KB) F2 gKB (Q) 17 An example of theorem preserving (and non model preserving) poly size reduction from updated knowledge bases to PL is given in [Win89]. The reduction shown in the previous example is also theorem preserving, using for g KB the identity function. We remark that our de nitions of reduction are more general than those proposed in [GKPS95] In particular, in [GKPS95] only a notion analogous to De nition 4 is considered, and only ....

M. Winslett. Sometimes updates are circumscription. In Proc. of IJCAI'89, pages 859-863, 1989.

.... persistency by stating special default rules ( HM87] In logic programming, various versions of negation as failure have been defined to specify that fluents persist if other fluents can not be proved to hold (see [BD99,GL93] In this paper we generalize a particular approach introduced in [Win88,Win89] and [Dal88] The overall framework is propositional logic with respect to an underlying signature L. We denote by Mod L the set of all propositional models with respect to L: Mod L is also called set of all worlds. The actual world can then be simply represented as an element of Mod L . In most ....

....oe with oe OE oe 0 . In order to handle the example above correctly, OE must be defined accordingly. In [Sch95b,BLS98] the authors state general representation results for preference relations between arbitrary sequences of models. A more intuitive approach to exclude such examples is due to [Win88,Win89]. The idea is to assume the notion of a distance between arbitrary worlds. Definition 5 (Distance dist dist dist) A distance dist is a function that associates to any two worlds a nonnegative rational number: dist : Mod L Theta Mod L Gamma I Q; A 1 ; A 2 ) 7 dist(A 1 ; A 2 ) The idea of ....

[Article contains additional citation context not shown here]

Marianne Winslett. Sometimes updates are circumscription. In Proc. 11th Int. Joint Conf. on Artificial Intelligence (IJCAI'89), pages 859--863, 1989.

....consistency. Recently, belief revision has received a lot of attention in AI, 1 which led to a number of different proposals for different applications (Ginsberg 1986; Ginsberg, Smith 1987; Dalal 1988; Gardenfors, Makinson 1988; Winslett 1988; Myers, Smith 1988; Rao, Foo 1989; Nebel 1989; Winslett 1989; Katsuno, Mendelzon 1989; Katsuno, Mendelzon 1990; Doyle 1990) Most of this research has been considerably influenced by approaches in philosophical logic, in particular by Gardenfors and his colleagues (Alchourr on, Gardenfors, Makinson 1985; Gardenfors 1988) who developed the logic of theory ....

Winslett, M. S. (1989): Sometimes Updates are Circumscription, in: Proceedings of the 11th International Joint Conference on Artificial Intelligence, Detroit, Mich., 859--863.

....further work By analytically deriving the KM postulates for update from a rigorous theory of action, we have linked two previously unrelated fields of research and provided a foundation for the KM update proposal. A formal connection between non monotonic reasoning and update was first studied in [Winslett, 1989], for Winslett s update operator, but with no relation to theories of action. She has also suggested in [Winslett, 1988] to use update for reasoning about action; our results can be seen as providing formal support to this proposal. Independently, Reiter, 1992] has proposed an account of database ....

Winslett, Marianne 1989. Sometimes updates are circumscription. In Proceedings of the 11th International Joint Conference on Artificial Intelligence.

....computing the updated database) Grahne and Mendelzon provide complexity results for subjunctive queries (see also [ Eiter and Gottlob, 1991 ] as well as algorithms to answer these queries under their model checking approach. Given the close connection between PMA update and circumscription ( Winslett, 1989, Del Val and Shoham, 1992 ] we are investigating the applicability of circumscriptive theorem provers (reviewed in [ Brewka, 1991 ] to answering subjunctive queries in clausal databases. Acknowledgements Thanks to Yoav Shoham and Marianne Winslett for detailed comments on a previous ....

Winslett, Marianne 1989. Sometimes updates are circumscription. In Proceedings of the 11th International Joint Conference on Artificial Intelligence.

....(this work is now under way) Another interesting direction would be to weaken appropriately the axioms for epistemic entrenchment so that the connection expressed by (E v) can be extended to partial PMA preorders as well. Finally, in view of the relation between the PMA and circumscription [10], one may use the connections established herein to provide a characterization of circumscription in terms of epistemic entrenchment. 8 Acknowledgments I am grateful to Hans Rott for many interesting discussions on this article during my stay in Konstanz. Many thanks also to Patrick Doherty, ....

Marianne Winslett. Sometimes updates are circumscription. In Proceedings of the Eleventh International Joint Conference on Artificial Intelligence, pages 859--863. Morgan Kaufmann, 1989. Detroit, Michigan.

.... belief revision has received a lot of attention in AI, 1 which led to a number of different proposals for different applications [ Ginsberg, 1986; Ginsberg and Smith, 1987; Dalal, 1988; Gardenfors and Makinson, 1988; Winslett, 1988; Myers and Smith, 1988; Rao and Foo, 1989; Nebel, 1989; Winslett, 1989; Katsuno and Mendelzon, 1989; Katsuno and Mendelzon, 1990; Doyle, 1990 ] Most of this research has been considerably influenced by approaches in philosophical logic, in particular by Gardenfors and his colleagues [ Alchourr on et al. 1985; Gardenfors, 1988 ] who developed the logic of ....

Marianne S. Winslett. Sometimes updates are circumscription. In Proceedings of the 11th International Joint Conference on Artificial Intelligence, pages 859--863, Detroit, Mich., 1989.

....[ Katsuno and Mendelzon, 1989; 1991 ] and specific operators have been proposed in [ Winslett, 1990 ] and [ Forbus, 1989 ] In this paper we investigate the relationship between circumscription and many operators for belief revision and update. A first study of these relations has been done in [ Winslett, 1989 ] where she relates her operator to circumscription. We expand her results showing similar connections between several other belief revision operators and circumscription. To this end, we also introduce a variant of circumscription based on cardinality, rather than set containment. The ....

....cardinality based variant on the other hand. Furthermore, we have pointed out the many benefits that the established correlations can deliver to the analysis of both fields. Our results greatly extends Winslett s results on transforming her revision operator into circumscription presented in [ Winslett, 1989 ] Even though Winslett s analysis could be further extended to deal with other operators, our results provide us with more direct and simple translations. Acknowledgments We want to thank Marco Cadoli and Francesco M. Donini for helpful discussions on the content of this paper. ....

M. Winslett. Sometimes updates are circumscription. In Proceedings of the Eleventh International Joint Conference on Artificial Intelligence (IJCAI-89), pages 859--863, 1989.

....for the facilitation of proof, Baker s circumscription policy can be translated into an equivalent, more easily understood, model based structure. The structure into which we will translate Baker s policy is based on those used in the belief update revision literature ( KM91] Marianne Winslett ([Win89]) has previously demonstrated that circumscription and update are related, by showing that update can be represented as circumscription. This translation goes the other way. A worlds structure is a tuple W = K,P,E,T,I where: K is a set of worlds , members of which are themselves subsets of P ....

Marianne Winslett. Sometimes updates are circumscription. In Proceedings of the International Joint Conference for Artifical Intelligence, pages 859--863, 1989.

....are translatable one into another, although such translation may lead to an exponential increase of the size of the formula. Most of the translations have Propositional Logic (PL) as their target formalism. e.g. BED91] from default logic to PL, BED94] from disjunctive logic programs to PL, [Win89] from revised knowledge bases to PL, GPP89] from circumscription to PL. Only very recently researchers started analyzing the space efficiency of PKR formalisms; this kind of investigation includes questions such as is exponential increase of the above mentioned translations intrinsic, or is it ....

....there exists a polynomial function g KB such that for every query Q on the variables of KB it holds that KB F 1 Q iff f(KB) F 2 g KB (Q) 136 CHAPTER 7. SUCCINCTNESS An example of theorem preserving (and non model preserving) polysize reduction from updated knowledge bases to PL is given in [Win89]. The reduction shown in the previous example is also theorem preserving, using for g KB the identity function. We remark that our definitions of reduction are more general than those proposed in [GKPS95] In particular, in [GKPS95] only a notion analogous to Definition 45 is considered, and only ....

M. Winslett. Sometimes updates are circumscription. In Proceedings of the Eleventh International Joint Conference on Artificial Intelligence (IJCAI-89), pages 859--863, 1989.

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M. Winslett. Sometimes updates are circumscription. In N. S. Sridharan, editor, Proceedings of the Eleventh International Joint Conference on Artificial Intelligence (IJCAI '89), pages 859--863, Detroit, Michigan, 1989. Morgan Kaufmann.

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