Kowalski, R. (1979). Algorithm = Logic + Control. Communications of the ACM 22(7), 424-436.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....language prototyping. However, traversal functionality is typically implemented in tangled fashion. Higher order predicates for list processing are folklore but not so for traversal schemes. The separation of logic and control has been advocated in Kowalski s seminal Algorithm = Logic Control [19], but this was never achieved for traversal control. Hence, we are motivated to incarnate strategies in Prolog. In fact, mapping the strategy semantics onto the Prolog language is straightforward. As an indication, in Fig. 5, we implement the all combinator, and everything else what is needed for ....

R. A. Kowalski. Algorithm = logic + control. Communications of the ACM, 22(7):424--436, July 1979.

....lower level reasoning mechanism, that solve prob lems by manipulating a rich representation that encodes all the application domain knowledge needed to solve the problem. These systems are based on the assumption of separating problem specification from problem solving behavior [Kowalski, 1979]. Once the knowledge is acquired and represented in the appropriate format, the problem is considered as solved. In practice, that is not exactly what happens. Besides the fact that the knowledge acquisition and knowledge repre sentation in a suitable form is a formidable task, the generality of ....

....description languages. The use of logic as a programming language has been the subject of research in the areas of logic programming and formal specification languages. Logic programming is based on the assumption that is possible to completely separate problem specification from problem execution [Kowalski, 1979]. It assumes a general problem solving mechanism, a theorem prover, capable of executing a logic specification. Two main problems with this approach are, first, logical notations are usually hard for most people to read and understand, second, some interesting prob lems in logical systems are ....

R.A. Kowalski. Algorithm = logic + control. Communications of the ACM, 22(7):424 436, July 1979.

....So far we have considered only purely connectionist approaches. But connectionist techniques may also supplement traditional AI systems in order to overcome their weaknesses. A theorem proving task can usually be divided into the logic of the problem and the control needed to find a proof [Kowalski, 1979]. Whereas it is comparatively easy to specify a problem as a logical 26 formula, it is much more difficult to specify control knowledge as this kind of knowledge is often domain dependent. In most automated theorem provers and logic programming systems the programmer has to provide some ....

R. A. Kowalski. Algorithm = logic + control. Communications of the ACM, 22:424--436, 1979.

....need to design a program. The undecidability of any reasonably powerful logic shows that there will be limitations on the expressiveness of such logic languages but even decidable logics like propositional calculus have unacceptably slow decision procedures. The approach most clearly espoused in [Kow79] is to use a de ned subset of general logic (Horn clauses) and to help the translator nd ecient search strategies by adding control information. One of the cornerstones of the Japanese Fifth Generation Programme was to make machines more usable by exploiting languages like Prolog . 64 There ....

R. Kowalski. Algorithm = logic + control. Communications of the ACM, 22:424-436, 1979.

....Derivation = Rules Strategies Alberto Pettorossi y and Maurizio Proietti z y DISP, Universit di Roma Tor Vergata, Roma, Italy. adp iasi.rm.cnr.it z IASI CNR, Roma, Italy. proietti iasi.rm. cnr.it Abstract In a seminal paper [38] Prof. Robert Kowalski advocated the paradigm Algorithm = Logic Control which was intended to characterize program executions. Here we want to illustrate the corresponding paradigm Program Derivation = Rules Strategies which is intended to characterize program derivations, rather than ....

....and in the works by Clark et al. Hogger, and Kowalski [11,12,32,39] for the case of logical languages. Similar ideas were proposed also in the case of imperative languages and one should mention, among others, the contributions of Dijkstra and Hoare (see, for instance, 21,31] In the paper [38] Kowalski proposes the motto: Algorithm = Logic Control, to promote a separation of concern when writing programs: a concern for correctness in the Logic component, and a concern for e ciency in the Control component. This separation idea for program development goes back to the seminal paper by ....

R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424436, 1979.

....of a program. 1 Introduction Virtuous programming methodology, which consists in focusing on correctness of programs at first and on their efficiency only afterwards, fits particularly well with the logic programming paradigm, as stated by the famous motto: Algorithm = Logic Control [Kow79] This encourages the application of transformation systems to logic programs both for synthesizing a correct program from a logic specification [Dev90] and for optimizing it [TS84] The main requirements for a practical transformation systems are on one hand to guarantee the preservation of ....

....termination since they are semantic conditions and operational in style, not decidable in general. 5 Conclusions Virtuous programming methodology which consists in focusing on correctness of programs at first and on their efficiency only afterwards, fits particularly well with logic programming [Kow79, Dev90] This encourages the application of transformation systems to logic programs both for synthesizing a correct program from a logic specification and for optimizing it. The main requirements for a practical transformation systems are on one hand to guarantee the preservation of interesting ....

R. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424--436, 1979.

....use of the characterized exception handling constructs. Keywords: Continuations, denotational semantics, exception handling, cut. 1 Introduction One of the main features of Logic Programming is the explicit distinction between the logic component and the control component of programs [Kow74, Kow79] The meaning of a program is completely specified by its logic component, which defines what the program does, independently of how the results are computed. According to this distinction, standard semantics have been defined for logic programs without taking into account the control 1 ....

R. A. Kowalski. Algorithm= logic + control. Communications of the ACM, 22(7):424--436, 1979.

....of the paper, we assess different areas related to theory and program development in Computational Logic. In particular: language implementation, program analysis and program transformation. We then discuss a novel view on the famous Algorithm = Logic Control equation of Robert Kowalski ([11]) which played an important role in theory and program development in the past. We then briefly comment on software engineering (or the lack of it in Computational Logic) and conclude with some promising future directions. 1.2 Implementation, analysis and transformation 1.2.1 Implementation ....

....support, such flexible control declaration languages could provide development tools that are in many ways similar to powerful program synthesis systems, such as the KIDS system of D. Smith ( 23] 1. 3 Algorithm = Logic Control revisited The Algorithm = Logic Control equation of [11] has motivated much work related to program development, especially in the context of program transformation and synthesis. In recent years, Robert Kowalski has revisited the equation, expressing that one should stress much more the procedural reading of logic programs, while reducing the emphasis ....

R.A. Kowalski. Algorithm = logic + control. Communications of the ACM, 22:424--431, 1979.

....or object oriented databases such meta information is even mandatory. For example, NP complete programs specified in DATALOG func neg need extra semantic heuristic control knowledge to achieve tractability. In the spirit of Kowalski s celebrated equation algorithm = logic control ([Kow79]) this paper proposes a mechanism for entering such semantic control knowledge into the query optimization process. In a first step here we concentrate on semantic knowledge in the form of subsumption information, which seems to be ubiquitous in applications. To mention just a few areas where ....

R. A. Kowalski. Algorithm = logic + control. Communications of the ACM, 22(7):424--436, Jul. 1979.

....one. Thus, input consuming programs are shown to be the right answer for conjugate eciency and declarativeness. Keywords: Logic programming, dynamic scheduling, semantics 1 Introduction Control in Logic Programming According to the widely known and accepted slogan Algorithm = Logic Control [13], a program can be regarded as 1 a logic speci cation together with a control mechanism for executing it. In this light, one of the inspiring ideas of the logic programming paradigm is to ask the programmer only the logic speci cation and leave the control part to the interpreter. As an example ....

R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424-436, 1979. 26

....Control technique and the Program Composition technique. 3.2. 1 Compiling Control One of the advantages of logic programming over conventional imperative programming languages is that by writing a logic program one may easily separate the logic part of an algorithm from the control part [97]. By doing so, the correctness of an algorithm w.r.t. a given speci cation is often easier to prove. Obviously, we are then left with the problem of providing an e cient control. Unfortunately, the naive Prolog strategy for controlling SLD resolution [103] does not always give us the desired ....

R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424 436, 1979.

....from Horn clauses of the form A A 1 ; An , with A; A 1 ; An being positive atoms. They can be considered as the heart of the logic programming paradigm because they possess a very simple and clear declarative semantics and a sound and complete operational semantics, namely SLD ([CKPR73,Kow74,Kow79]) The problem is that almost any application goes beyond the limits of definite clauses. Normal programs extend definite programs by allowing negation : The logic programming community has decided to use some variants of negation as failure (NAF) if A is a ground atom the goal :A succeeds if A ....

R. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22:424--436, 1979.

....various papers of the collection. In particular he identifies three major difficulties. As discussed in [11] a first difficulty comes from splitting the heuristic and the epistemological part of intelligence. The starting point of the discussion is Kowalski s equation ALGORITHM = LOGIC CONTROL [36], an equation which resembles the distinction between the epistemological part and the heuristic part of intelligence. As stated at the very beginning of [11] The formula isn t precise, and it won t be until someone proposes a precise and generally accepted notion of how control is to be added ....

R. Kowalski. Algorithm = logic + control. Communications of the ACM, 22(7):424--436, 1979.

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R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424--436, 1979.

....assumption that low level reactive control is inherently alogical. This paper challenges this assumption. This paper investigates the idea of using logic programs as a representation for the control of autonomous robots. This should be seen as logic programming in the sense of logic control [Kowalski, 1979] ; we use a logic program to specify what to do at each time, and use an execution mechanism that exploits a derived notion of state in order to make it practical. The main highlights of this approach are: 1. An agent can be seen as a transduction: a function from inputs (sensor values) into ....

R. Kowalski. Algorithm = logic + control. Communications of the ACM, 22:424--431, 1979.

....is now considered well established, having been studied for several decades [1, 17] Over these years, researchers have distinguished at least two basic categories of semantics for logic programming: declarative and operational. Following the idea that logic programming is logic control [16], a number of researchers have found it convenient to dedicate their investigation not to the declarative semantics of logic programming, but rather to the study of the various control ow concepts encountered therein, an approach usually called logic programming without logic that is advocated ....

R. Kowalski. Algorithm = logic + control. Communications of the ACM, 22:424-435, 1979.

....one. Thus, input consuming programs are shown to be the right answer for conjugate eciency and declarativeness. Keywords: Logic programming, dynamic scheduling, semantics 1 Introduction Control in Logic Programming According to the widely known and accepted slogan Algorithm = Logic Control [1], a program can be regarded as 1 a logic speci cation together with a control mechanism for executing it. In this light, one of the inspiring ideas of the logic programming paradigm is to ask the programmer only for the logic speci cation and leave the control part to the interpreter. As an ....

R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424-436, 1979.

....preference knowledge separate from programming knowledge. This means that a control part which determines strategies for problem solving is separated from a logic part which specifies a declarative background knowledge. Such a separation accords with Kowalski s principle of logic programming [33]. We introduced PLP under the answer set semantics, while an analogous mechanism is easily devised for other semantics of logic programming. 14 Grosof [23] introduced a generalized circumscription having pre order priority relations over first order predicates. 41 From the AI side, PLP can ....

R. A. Kowalski, Algorithm = Logic + Control, Communications of the ACM 22(1979) 424--435.

....derivations of simply moded programs. Finally, for this class of programs, we provide a necessary and sucient criterion for termination. 1 Introduction 1.1 Background Logic programming is based on giving a computational interpretation to a fragment of rst order logic. Kowalski [12] advocates the separation of the logic and control aspects of a logic program and has coined the famous formula Algorithm = Logic Control. The programmer should be responsible for the logic part. The control should be taken care of by the logic programming system. In reality, logic ....

R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424-436, 1979.

....derivations of simply moded programs. Finally, for this class of programs, we provide a necessary and sufficient criterion for termination. 1 Introduction Background. Logic programming is based on giving a computational interpretation to a fragment of first order logic. Kowalski [14] advocates the separation of the logic and control aspects of a logic program and has coined the famous formula Algorithm = Logic Control. The programmer should be responsible for the logic part. The control should be taken care of by the logic programming system. In reality, logic ....

R. A. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424--436, 1979.

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Kowalski, R. (1979). Algorithm = Logic + Control. Communications of the ACM 22(7), 424-436.

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Kowalski, R. A. (1979). Programming = logic + control. Communications of the ACM, 22(7):424--436.

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R. Kowalski, Algorithm = Logic + Control, Communications of ACM 22 (1979), 424-436.

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R. Kowalski. Algorithm = logic + control. Communications of the ACM, 22:424--436, 1979.

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R. Kowalski. Algorithm = Logic + Control. Communications of the ACM, 22(7):424--436, July 1979.

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