J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93--147, 1995.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... been found equivalent to the well founded semantics for extended logic programs, WFSX [16, 2] This paper makes the following contributions: we de ne a least xpoint argumentation semantics for extended logic programs, and show its equivalence to the well founded semantics with explicit negation [16, 2, 1]. In order to relate this semantics to other argumentation semantics, we set up a general framework to classify notions of justi ed arguments, and use it to compare our argumentation semantics to those of Dung [6] and Prakken and Sartor [17] among others. We develop a general dialectical proof ....

....di er, and both di er from u=a justi ability, which will be shown equivalent to the well founded semantics WFSX [16, 2] in the following section. 4 Well founded semantics We recollect the de nition of the well founded semantics for extended logic programs, WFSX. We use the de nition of [1], because it is closer to our de nition of argumentation semantics than the original de nition of [16, 2] De nition 8 The set of all objective literals of a program P is called the Herbrand base of P and denoted by H(P ) A pseudo interpretation of a program P is a set T [ not F where T and ....

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J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93-147, 1995.

....11 Let P be an extended logic program and WFM(P ) its well founded model [2] Then WFM(P ) L there exists a u a justified argument for L # not all arguments for L are attacked by a u a justified argument . Proof (Sketch) For the sake of brevity we can only sketch the proof. In [1], the well founded model is defined as the least fixpoint of the operator ##s , where # is the Gelfond Lifschitz operator [9] and #s is the same operator applied to the semi normal version of the program, obtained by adding not to the body of each rule with head L. The fixpoint is generated by ....

....logic programs [2] The results concerning the relationships as depicted in Fig. 3 have been valuable in identifying such a semantics, as well as relating it to existing semantics. Furthermore the equivalence of J u a and WFSX allow the use of the efficient top down proof procedure for WFSX [1] to compute justified arguments in J u a . Future research will determine how to adapt this proof procedure to different argumentation semantics and its relation to dialogue games as defined in [7, 13, 16, 11] It is also an open question how the hierarchy changes when priorities are added as ....

J. J. Alferes, C. V. Dam asio, and L. M. Pereira, `A logic programming system for non-monotonic reasoning', Journal of Automated Reasoning, 14(1), 93--147, (1995).

....Trying to prove p in P 1 Prolog applies the rule p p over and over again. A similar reason stops P 2 from terminating in Prolog. The problems occur in general due to positive or negative loops through recursion. To deal with this problem we de ne T and TU trees, to prove verity and non falsity [ADP94a, ADP94b, ADP95, AP96]. De nition 8 Fuzzy T tree, TU tree Let P be a ground fuzzy extended logic program, let true be a new unary predicate symbol, and let P 0 be the program obtained from P by replacing rules of the form L with L true(1) and rules of the form L : V with L true(V ) A fuzzy T tree (resp. ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93-147, 1995.

....of G, a new rule G # # not G is introduced with a new atom G # . Then, an antiexplanation of G can be obtained as a credulous explanation of G # . 6 On the other hand, negative or mixed (anti )explanations cannot be directly computed by other abductive procedures. Alferes, Damasio and Pereira [2,10] propose an abductive framework within the three valued semantics in a di#erent way. Abduction is performed in their revision system to remove a contradiction in a program by changing the truthvalue of abducible literals into true, false or undefined, in which the change from true to ....

....value of an abducible is due to their three valued semantics, which very roughly corresponds to the situation that true is assigned to the abducible in some stable model and false is also assigned to it in another stable model. Their abductive framework is computed using their top down procedure [2], but they do not produce a transaction program. Usually, top down procedures like [23,10 12] compute one explanation at a time, but the minimality of an abductive explanation is not guaranteed in general. Our fixpoint operator in Definition 3.3, on the other hand, involves computation of all ....

J. J. Alferes, C. V. Damasio and L. M. Pereira, A logic programming system for nonmonotonic reasoning, J. Automated Reasoning, 14 (1995) 93--147.

....for NLP is computed by using an argument based approach, which has many similarities with DeLP [CS99] Many semantics for extended logic programs view default negation and symmetric negation as unrelated. To overcome this situation a semantics WFSX for extended logic programs has been defined [ADP95]. Well founded Semantics with Explicit Negation (WFSX) embeds a coherence principle providing the natural missing link between both negations: if L holds then notL should hold too (similarly, if L then not L) In DeLP this coherence principle also holds [GSC98] Finally, it must be remarked ....

J. J. Alferes, Carlos Viegas Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....semantics for NLP is computed by using an argument based approach, which has many similarities with DeLP [CS99] Many semantics for extended logic programs view default negation and symmetric negation as unrelated. To overcome this situation a semantics WFSX for extended logic programs was de ned [ADP95]. Well founded Semantics with Explicit Negation (WFSX) embeds a coherence principle providing the natural missing link between both negations: if L holds then not L should too (similarly, if L then not L) In DeLP this coherence principle also holds [GSC98] Finally, it must be remarked ....

J. J. Alferes, Carlos Viegas Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93-147, 1995.

....for NLP is 25 computed by using an argument based approach, which has many similarities with DeLP [CS99] Many semantics for extended logic programs view default negation and symmetric negation as unrelated. To overcome this situation a semantics WFSX for extended logic programs has been de ned [ADP95]. Well founded Semantics with Explicit Negation (WFSX) embeds a coherence principle providing the natural missing link between both negations: if L holds then not L should hold too (similarly, if L then not L) In DeLP this coherence principle also holds [GSC98] Finally, it must be ....

J. J. Alferes, Carlos Viegas Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93-147, 1995. 26

.... More general and more ecient methods of computing the entailment of L 1 and its extensions should be found. One possibility is to investigate other inference mechanisms which are sound w.r.t. declarative logic programming semantics. For programs with unique answer sets, the SLX procedure from [ADP94, ADP95] is a promising candidate. It computes answers w.r.t. the well founded [VGRS91, PAA92] semantics of logic programs and hence is sound w.r.t. the answer set semantics. An interesting and challenging problem is to expand SLX by allowing disjunction and therefore reasoning by cases. Another ....

J. Alferes, C. Damasio, and L Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning (special issue), 1995.

....1 Introduction Well founded semantics was introduced in [17] to provide 3 valued interpretations to logic programs with negation. Since its introduction, the well founded semantics has become one of the most widely studied and most commonly accepted approaches to negation in logic programming [1, 9, 5, 6, 18, 3]. It was implemented in several top down reasoning systems, most prominent of which is XSB [14] Well founded semantics is closely related to the stable model semantics [11] another major approach to logic programs with negation. The well founded semantics approximates the stable model semantics ....

J.J. Alferes, C.V. Dam'asio, and L.M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14:93--147, 1995.

....manner as deductive databases [25] These properties of tabling provide a basis for programming with nonmonotonic constructs. Consider implementation of a class of programs that is embeddable into the well founded semantics, for instance the well founded semantics with explicit negation (WFSX) [2]. Using the embedding, a tabled meta interpreter can be written for the program, and partial deduction applied to the meta interpreter to produce an efficient implementation. Thus the representational power of non monotonic extensions like explicit negation becomes available to programmers solving ....

....was not approaching. This can be written as cross : train. Where the operator 1 denotes explicit negation. Explicit negation has been studied by a number of authors (see [16] for a summary of this work) here we consider programming the Well Founded Semantics with Explicit Negation or WFSX [2]. The key idea behind WFSX is the enforcement of the coherence principle, which, informally, states that the default negation of a statement is entailed by its explicit negation. WFSX has well understood relations with other semantics for explicit negation, such as answer sets [28] Furthermore, ....

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J. Alferes, C. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....working directory, and contains the de nitions of the predicates concat 3 and qsort 2, both of which are exported. compile(quick sort) Compiling . quick sort] quick sort compiled, cpu time used: 1.439 seconds] yes import concat 3, qsort 2 from quick sort. yes concat( 1,3] [2], L) qsort(L, S) L = 1,3,2] S = 1,2,3] yes. The standard predicate import 1 does not load the module containing the imported predicates, but simply informs the system where it can nd the de nition of the predicate when (and if) the predicate is called. 3.5 Command Line Arguments There ....

....the de nitions of the predicates concat 3 and qsort 2, both of which are exported. compile(quick sort) Compiling . quick sort] quick sort compiled, cpu time used: 1.439 seconds] yes import concat 3, qsort 2 from quick sort. yes concat( 1,3] 2] L) qsort(L, S) L = [1,3,2] S = 1,2,3] yes. The standard predicate import 1 does not load the module containing the imported predicates, but simply informs the system where it can nd the de nition of the predicate when (and if) the predicate is called. 3.5 Command Line Arguments There are several command line options ....

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J. Alferes, C. Damasio, and L. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 1995.

....Using WFSX for psychiatric assesment. ffl Case study: Using tabled aggregation for preferences and quantitative reasoning. 3 Overview ffl Tabling can form a means of implementing the Well Founded Semantics [127] and its extensions such as the Well Founded Semantics with Explicit Negation [3, 5], or Disjunctive Logic Programs under various semantics. ffl Tabling can be used as a preprocessor for stable models and extensions [56, 57] or can compute these models directly by means of abduction [34, 6] ffl Tabling can be used as a means to aggregate solutions for annotation logics ....

J. Alferes, C. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....spirit of the Horn logic programming paradigm. Namely, in each of these approaches, a program speci es extensions of predicates in a single intended model perfect or well founded, respectively. Moreover, suitably modi ed versions of resolution were proposed as a uniform processing mechanisms [ADP95,RRS 97] However, both these approaches lead to problems with excessive expressive power. Apt and Blair [AB90] proved that strati ed programs with nite number of strata specify precisely arithmetic sets. This means that they are expressive beyond what is at present considered computable. ....

....form of resolution can be applicable in the general case of skeptical semantics, without drastic restrictions on the syntax of programs. Whereas in the case of wellfounded semantics conditions limiting the complexity are known and resolutionbased systems for well founded semantics were developed [ADP95,RRS 97] in the case of skeptical semantics such results have yet to be established. 3 Stable logic programming In this section, we propose an alternative paradigm to that of the Horn logic programming, a paradigm consistent with the properties of stable models. We will refer to it as ....

J.J. Alferes, C.V. Damasio, and L.M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14:93-147, 1995.

....stable model of P iff Phi P (I) I (see [ AP96 ] for the definition of the Phi operator) The well founded model of the program P is the Fleast partial stable model of P . The well founded semantics of P is determined by the set of all partial stable models of P: Pereira et al. AP96; ADP95 ] showed that every non contradictory program has a well founded model and they also presented a complete and sound top down proof procedure for several classes of programs. In their work, Pereira et al. proposed a revision process that restores consistency for contradictory programs, taking ....

Jos'e J'ulio Alferes, Carlos Dam'asio, and Lu'is Moniz Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14:93--147, 1995.

....of the contradiction removal models in the lower semi lattice made of Contradiction Removal Models ordered by their supportive hypotheses. 34 4. 4 Dealing with Contradiction: Related Work The problem of removing contradiction from inconsistent programs has been approached by many authors (e.g. [57, 60, 4, 7, 8, 9, 53, 62, 67]) In this section, we consider other approaches coping with contradiction. In order to give meaning to a program, two main approaches can be followed. One is contradiction removal, in which hypotheses are discarded (possibly in a minimal way) in order to restore the non contradictoriness of a ....

.... refinement (dealing with contradiction) of the argumentation approach has been defined in [38] Besides relating our work with these semantics, we will also relate our approach with other semantics considering explicit negation rather than pseudo negation and based on contradiction removal [57, 60, 58, 4, 9] or contradiction avoidance [7, 8] 4.4.1 Argumentation Semantics Dung shows in [39] that the most of the approaches to non monotonic reasoning in artificial intelligence and logic programming can be expressed as different forms of argumentation. This idea is applied in [35] to develop a simple, ....

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J.J. Alferes, C. V. Damasio, and L.M. Pereira. A Logic Programming System for Nonmonotonic Reasoning. Journal of Automated Reasoning (14):93--147, 1995.

....table the meta interpreter. table demo 1. demo(true) demo( A,B) demo(A) demo(B) demo(not A) not demo(A) demo(A) clause(A,B) demo(B) ffl Note Use of cuts with tabled predicates 70 Negation A meta interpreter for well founded semantics with explicit negation (WFSX) [3] demo( true) demo(X) A,B) demo(X) A) demo(X) B) demo(t) not(A) not(demo(tu) A) demo(tu) not(A) not(demo(t) A) demo(t) A) rule(A,B) demo(t) B) demo(tu) A) rule(A,B) demo(tu) B) exchange(A,Aopp) demo(tu) not(Aopp) exchange( B,B) exchange(B, B) ffl ....

J. Alferes, C. Damasio, and L. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 1995.

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J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93--147, 1995.

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J. J. Alferes, C. V. Dam asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93--147, 1995.

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J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the JAR, 1995. To appear.

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J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93--147, 1995.

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Alferes, J. A., C. Damasio and L. M. Pereira. 1995. "A logic programming system for non-monotonic reasoning", Journal of Automated Reasoning 14: 93-147.

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J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93-147, 1995.

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Alferes, J. A., C. Damasio and L. M. Pereira. 1995. "A logic programming system for non-monotonic reasoning," Journal of Automated Reasoning 14: 93-147.

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J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93--147, 1995.

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J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. J. of Automated Reasoning, 14(1):93--147, 1995.

....denote the formula , where A 1 . Am and B 1 ; Bn are, respectively, the isotonic and antitonic occurrences, of propositional symbols in in the order they appear in (left to right) Regarding the semantics, we follow a paraconsistent and paracomplete approach inspired by WFSX p [3, 6], one of the well founded based semantics proposed for extended logic programs. A technique used in logic programming literature resorts to the notion of partial interpretation, requiring rst the usual notion of interpretation. De nition 8 (Interpretation) Consider a bilattice B = hB; t ; ....

.... M i of P complies with the Coherence Principle i for every propositional symbol A appearing in the language of P , d M (A) k d M ( A) Given these arguments, and in order to enforce coherence, we will resort to the semi normal gamma operator, inspired by the approach taken in [3, 6]: De nition 15 (Semi normal Gamma operator) Let P be a paraconsistent logic program and J an interpretation. The semi normal immediate consequences operator T I ; J ( k A) j A 2 P We also de ne (J) lfp T Mark that coherence is enforced in every propositional ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Special Issue of the Journal of Automated Reasoning, 14(1):93-147, 1995.

....turned out to be a promising approach to cope with negation by default. Subsequent work extended well founded semantics with a form of explicit negation and constraints [19] and showed that the richer language, called WFSX, is appropriate for a spate of knowledge representation and reasoning forms [2, 5]. In particular, the technique of contradiction removal of extended logic programs [20] opens up many avenues in model based diagnosis [5, 24] Definition 1. Extended Logic Program An extended logic program is a (possibly infinite) set of rules of the form L 0 L 1 ; Lm ; notLm 1 ; ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

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) J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14:93-147, 1995.

....the application of a contradiction removal process based on revising assumptions, possibly adopting of some other assumptions instead. This too has been extensively studied in AI and in the LP setting, and as a result automated reasoning systems have been made available which do that work for us [1]. 5.10 Updating Last but not least, work in LP has concerned itself with the updating of a knowledge base by another one. This notion of knowledge updating, as opposed to that of simple fact updating, opens up another dimension to the dynamics of logic, in contradistinction to the statics of the ....

J.Alferes, C.Damasio, L.Pereira, "A logic programming system for non-monotonic reasoning". J. Automated Reasoning, 14:93-147, 1995.

.... all extensions of a state of the art diagnoser, such as preferences and strategies [FNS94,NFS95] can be incorporated into the existing approach [DNPS95] The more recent second implementation of REVISE is based on a new top down evaluation of well founded semantics with explicit negation (WFSX) [ADP94a,ADP94b,ADP95], which lead to a dramatic speed increase. The REVISE system is embedded into an architecture for a diagnosis agent consisting of three layers: a knowledge base, an inference layer, and on top a component for communication and control (see Fig. 1) The core of the inference machine is the REVISE ....

....out to be a promising approach to cope with negation by default. Subsequent work extended well founded semantics with a form of explicit negation and constraints [PA92] and showed that the richer language, called WFSX, is appropriate for a spate of knowledge representation and reasoning forms [PAA93,PDA93,ADP95]. In particular, the technique of contradiction removal from extended logic programs [PAA91] opens up many avenues in model based diagnosis [PDA93,DNP94,DNPS95,MA95] Definition 1. Extended Logic Program An extended logic program is a (possibly infinite) set of rules of the form L 0 L 1 ; ....

[Article contains additional citation context not shown here]

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....[8] turned out to be a promising approach to cope with negation by default. Subsequent work extended well founded semantics with a form of explicit negation [11, 4] defining WFSX , and showed that the richer language is appropriate for a spate of knowledge representation and reasoning forms [9, 10, 3]. Definition 2.1 An extended logic program is a (possibly infinite) set of ground rules of the form L 0 L 1 ; L l ; not L l 1 ; not Lm (0 l m) where each L i is an objective literal (0 i m) If n = 0 then the rule is called a fact and the arrow symbol is ommited. An ....

....we review WFSX [4] a semantics for extended logic programs. For similarity with Prakkens s argumentation, instead of the declarative (bottom up) original definition of WFSX , we present an equivalent top down inference operator for WFSX . The equivalence between the definitions is shown in [3]. The inference operator has three parameters M , LA, and GA, where M is either t or tu indicating that we want to prove verity (t) and non falsity (tu) and LA and GA are lists of local and global ancestors that allow to detect negative and positive loops which lead to inference of non falsity ....

[Article contains additional citation context not shown here]

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....addressed [14, 23, 24] Program updating is distinct from program revision, where a program accommodates, perhaps non monotonically by revising assumptions, additional information about a world state. Work on logic programs revision (or contradiction removal) has received more attention (e.g. in [3, 5, 22, 40, 41]) A key insight into the issue of updating theories is due to Winslett [39] who showed that, contrary to theory revision, one must consider the e ect of an update in each of the states of the world that are consistent with our current knowledge of its state. The following realistic situation ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14:93-147, 1995.

....satisfied constraints, thus improving the fitness, as required by the notion of Lamarckian operator. To find support sets we need to know which literals belong to the model of a program. This information is obtainable through some sound and correct procedure for WFSXp such as the one described in [ADP95], or the one in [APS99] In the case of the circuit diagnosis problems in section 4, the support sets procedure becomes simplified in that the occurrences of default negated literals pertain only to revisables. When computing the support sets, the Lamarckian operator also modifies an extra bit ....

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14:93--147, 1995.

....out to be a promising approach to cope with negation by default. Subsequent work extended well founded semantics with a form of explicit negation and constraints [11,4] and showed that the richer language, called WFSX, is appropriate for a spate of knowledge representation and reasoning forms [9,10,3]. Definition 1. Extended Logic Program, Integrity Constraint An extended logic program is a (possibly infinite) set of rules of the form L 0 L 1 ; L l ; not L l 1 ; not Lm (0 l m) where each L i is an objective literal (0 i m) An objective literal is either an atom A or its ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....ed constraints, thus improving the tness, as required by the notion of Lamarckian operator. To nd the support sets we need to know which literals belong to the model of a program. This information is obtainable through some sound and correct procedure for WFSXp such as the one described in [1], or the one in [4] In the case of the circuit diagnosis problems in section 4, the support sets procedure becomes simpli ed in that the occurrences of default negated literals in the program pertain only to revisables. The algorithm implementing the Learn operator is given below. procedure ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14:93-147, 1995.

....satisfied constraints, thus improving the fitness, as required by the notion of Lamarckian operator. To find support sets we need to know which literals belong to the model of a program. This information is obtainable through some sound and correct procedure for WFSXp such as the one described in [3], or the one in [6] In the case of the circuit diagnosis problems in section 4, the support sets procedure becomes simplified in that the occurrences of default negated literals pertain only to revisables. When computing the support sets, the Lamarckian operator also modifies an extra bit ....

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14:93--147, 1995.

....of a contradiction removal process based on revising assumptions, possibly adopting of some other assumptions instead. This too has been extensively studied in AI and in the logic programming setting, and as a result automated reasoning systems have been made available which do that work for us[1, 13] and have been applied to real domains[22] 5.10 Updating Last but not least, work in logic programming has concerned itself with the updating of a knowledge base by another one. This notion of knowledge updating, as opposed to that of simple fact updating, opens up another dimension to the ....

Jose Julio Alferes, Carlos V. Damasio and Lus Moniz Pereira, "A logic programming system for non-monotonic reasoning". Journal of Automated Reasoning, 14:93-147, 1995.

....addressed [22,23,14] Program updating is distinct from program revision, where a program accommodates, perhaps non monotonically by revising assumptions, additional information about a world state. Work on logic programs revision (or contradiction removal) has received more attention (e.g. in [3,21,5,38,37]) A key insight into the issue of updating theories is due to Winslett [36] who showed that, contrary to theory revision, one must consider the e ect of an update in each of the states of the world that are consistent with our current knowledge of its state. The following realistic situation ....

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14:93-147, 1995.

....worked out in a similar fashion. We can now state our first main result. The most important semantics surveyed here coincide on the class of definite extended logic programs. Theorem 3. Let P be a definite extended logic programs. Apart from syntactical differences, all the semantics reported in [8, 43, 50, 37, 1, 2, 52], and Wagner s logic programs with strong negation [60] and with liberal reasoning [59] are isomorphic to MP . The above theorem fully characterizes the several semantics of definite extended logic programs in terms of the fixpoint semantics given in Definition 2. 3.2 Model theoretic semantics ....

....only three valued extended logic programming semantics, and in the next section the two valued ones. Two paraconsistent extensions of Well Founded Semantics are presented, namely Sakama s extended well founded semantics and our own paraconsistent Well Founded Semantics with Explicit Negation [1, 10], WFSX p . We conclude by studying Wagner s Vivid Knowledge Bases under liberal reasoning [59, 60] 4.1 Sakama s Extended Well founded Semantics and Przymusinski s Extended Stable Semantics The first attempt to introduce explicit negation into well founded semantics was made by Przymusinski in ....

[Article contains additional citation context not shown here]

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

No context found.

J. J. Alferes, C. V. Damasio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....satisfied constraints, thus improving the fitness, as required by the notion of Lamarckian operator. To find support sets we need to know which literals belong to the model of a program. This information is obtainable through some sound and correct procedure for WFSXp such as the one described in [3], or the one in [6] In the case of the circuit diagnosis problems in section 4, the support sets procedure becomes simplified in that the occurrences of default negated literals pertain only to revisables. When computing the support sets, the Lamarckian operator also modifies an extra bit ....

Alferes, J. J., C. V. Dam'asio, and L. M. Pereira: 1995, `A Logic Programming System for Non-monotonic Reasoning'. Journal of Automated Reasoning 14, 93--147.

....representation literature that information that is assumed false because there is no evidence to support it can be represented by default negation; while information that is explicitly known to be false can be represented by explicit negation. The well founded semantics with explicit negation [1], provides a semantics for adding explicit negation to the well founded semantics. This semantics can be evaluated using a linear transformation of rules with explicit negation into normal logic program rules. 3.3 Speculative Information Speculative information, such as that needed to conclude ....

....In addition, preferences can be declared on preferences themselves. Since [P; P ref ] norm is an extended program, it can be evaluated under any semantics for extended programs. For the purposes of this paper, we restrict our attention to the well founded semantics with explicit negation [1]. It is immediate from De nition 1 that an objective literal that depends on cyclic preferences (i.e. an objective literal A such that prefer(A; A) is true) will either be false or unde ned in the extended well founded model of [P; P ref ] WFM ( P; P ref ] 4.1 Relation to other Preference ....

J. Alferes, C. Damasio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93-147, 1995.

....be represented by default negation; while information that is explicitly known to be false can be represented by explicit negation. Explicit negation can be added to the well founded semantics without increasing its computational complexity under the well founded semantics with explicit negation [1] and directly embedded into the well founded semantics [6] 3.3 Speculative Information More speculative information, such as that needed to conclude an Adjustment Disorder can be represented using abduction, which allows hypothetical reasoning. Since preference rules can be 2 The psychiatric ....

J. Alferes, C. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

No context found.

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....be represented by default negation; while information that is explicitly known to be false can be represented by explicit negation. Explicit negation can be added to the wellfounded semantics without increasing its computational complexity under the well founded semantics with explicit negation [1] and directly embedded into the well founded semantics [6] 3.3 Speculative Information More speculative information, such as that needed to conclude an Adjustment Disorder can be represented using abduction, which allows hypothetical reasoning. Since preference rules can be transformed into ....

J. Alferes, C. Dam'asio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

....it. This corresponds to the usual approach in mathematical logic, and of several of the semantics for extended logic programs [32, 17, 25] Belief revision approach: The program is revised in order to regain consistency. This is the view adopted by some authors in the logic programming community [30, 26, 28, 1]. It does not necessarily require an explicit paraconsistent semantics: the procedural program transforming revision operators suffice. Paraconsistent approach: Accept contradictory information into the semantics and perform reasoning tasks that take it into account[7, 23, 24, 21, 22, 37, 38, 1] ....

....community [30, 26, 28, 1] It does not necessarily require an explicit paraconsistent semantics: the procedural program transforming revision operators suffice. Paraconsistent approach: Accept contradictory information into the semantics and perform reasoning tasks that take it into account[7, 23, 24, 21, 22, 37, 38, 1]. This is the approach we will further explore in this paper. The first approach only makes sense when dealing with mathematical objects. For instance, if we have a large knowledge base being maintained or updated by different agents, it is natural to encounter inconsistencies in the database. ....

[Article contains additional citation context not shown here]

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

No context found.

Jos'e J'ulio Alferes, Carlos Dam'asio, and Lu'is Moniz Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14:93--147, 1995.

No context found.

J. Alferes, C. Damasio, and L. M. Pereira. A logic programming system for nonmonotonic reasoning. Journal of Automated Reasoning, 14(1):93-147, 1995.

No context found.

J. J. Alferes, C. V. Dam'asio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, Feb. 1995.

No context found.

J. J. Alferes, Carlos Viegas Damasio, and L. M. Pereira. A logic programming system for non-monotonic reasoning. Journal of Automated Reasoning, 14(1):93--147, 1995.

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