perm filename ABS3[BIB,CSR] blob sn#422928 filedate 1979-03-07 generic text, type C, neo UTF8

COMMENT ⊗ VALID 00015 PAGES C REC PAGE DESCRIPTION C00001 00001 C00002 00002 .DEVICE XGP C00003 00003 .once center C00005 00004 .begin nofill <<CS-710>> C00008 00005 .begin nofill <<CS-711>> C00012 00006 .begin nofill <<CS-712>> C00013 00007 .begin nofill <<CS-713>> C00015 00008 .begin nofill <<AIM-322>> C00018 00009 .begin nofill <<CS-717>> C00020 00010 .begin nofill <<AIM-323>> C00021 00011 .begin nofill <<CS-719>> C00023 00012 .begin nofill <<CS-720>> C00024 00013 .begin nofill <<CS-721>> C00026 00014 .begin nofill <<CS-722>> C00029 00015 .begin nofill <<CS-723>> C00032 ENDMK C⊗; .DEVICE XGP; . .turn on "↔" for "→" .turn on "%,π,α,#,&,∂,↑,↓,[,]" .turn on "∩" for "↑" .turn on "∪" for "↓" . .font 1 "nonm"; .font 2 "baxm30"; .font 3 "math30"; .font 4 "fix25"; .font 5 "grkl30"; . .sides←1; .require "twocol.pub[sub,sys]" source file; . .SELECT 1 .at "@" ⊂"####"⊃ .at "|cd" ⊂"%3α*%*"⊃ .at "≤" ⊂"%4α≤%*"⊃ . .at "!!" txt ";" ⊂ .("txt"[1]&"∩["&"txt"[2]&"]&∪[ "&"txt"[3]&"]"); . ⊃ . .PLACE TEXT; . .next page .once center %1MOST RECENT CS REPORTS - 1979 No. 3↔(month) @Listed below are abstracts of the most recent reports published by the Computer Science Department of Stanford University. @TO REQUEST REPORTS: Check the appropriate places on the enclosed order form, and return the entire order form page (including mailing label) by June 29, 1979. In many cases we can print only a limited number of copies, and requests will be filled on a first come, first serve basis. If the code (FREE) is printed on your mailing label, you will not be charged for hardcopy. This exemption from payment is limited primarily to libraries. (The costs shown include all applicable sales taxes. PLEASE SEND NO MONEY NOW, WAIT UNTIL YOU GET AN INVOICE.) @ALTERNATIVELY: Copies of most Stanford CS Reports may be obtained by writing (about 2 months after MOST RECENT CS REPORTS listing) to NATIONAL TECHNICAL INFORMATION SERVICE, 5285 Port Royal Road, Springfield, Virginia 22161. Stanford Ph.D. theses are available from UNIVERSITY MICROFILMS, 300 North Zeeb Road, Ann Arbor, Michigan 48106. .begin nofill --↔-- --↔-- .end .begin nofill <<CS-710>> STAN-CS-79-710 @NUMERICAL COMPUTATION OF THE SCHWARZ-CHRISTOFFEL TRANSFORMATION Author: Lloyd Trefethen 42 pages↔Cost: $2.90 .end @ABSTRACT: A program is described which computes Schwarz-Christoffel transformations that map the unit disk conformally onto the interior of a bounded or unbounded polygon in the complex plane. The inverse map is also computed. The computational problem is approached by setting up a nonlinear system whose unknowns are essentially the unknown "accessory parameters" z↓k, and solving this system with a standard subroutine. @New features of this work include the evaluation of integrals within the disk rather than along the boundary, making possible the treatment of unbounded polygons; the use of a compound form of Gauss-Jacobi quadrature to evaluate the Schwarz-Christoffel integral, making possible high accuracy at reasonable cost; and the elimination of constraints in the nonlinear system by a simple change of variables. @Application of the Schwarz-Christoffel transformation may lead to practical methods for solving the Laplace and Poisson equations accurately in two-cimensional problems with irregular or unbounded (but not curved or multiply connected) geometrices. Computational examples are presented. The time required to solve the mapping problem is roughly proportional to N↑3, where N is the number of vertices of the polygon. A typical set of computations to 8-place accuracy with N %3≤%1 10 takes 1-10 seconds on an IBM 370/168. .skip .begin nofill <<CS-711>> STAN-CS-78-711 @VERSION SPACES: AN APPROACH TO CONCEPT LEARNING Author: Tom Michael Mitchell↔(Thesis) 216 pages↔Microfiche only. .end @ABSTRACT: A method is presented for learning general descriptions of concepts from a sequence of positive and negative training instances. This method involves examining a predetermined space or language of possible concept descriptions, finding those which are consistent with the observed training instances. Rather than use heuristic search techniques to examine this concept description space, the subspace (version space) of all plausible concept descriptions is represented and updated with each training instance. This version space approach determines all concept descriptions consistent with the training instances, without backtracking to reexamine past training instances or previously rejected concept descriptions. @The computed version space summarizes the information within the training instances concerning the identity of the concept to be learned. Version spaces are therefore useful for making reliable classifications based upon partially learned concepts, and for proposing informative new training instances to direct further learning. The uses of version spaces for detecting inconsistency in the training instances, and for learning in the presence of inconsistency are also described. @Proofs are given for the correctness of the method for representing version spaces, and of the associated concept learning algorithm, for any countably infinite concept description language. Empirical results obtained from computer implementations in two domains are presented. The version space approach has been implemented as one component of the Meta-DENDRAL program for learning production rules in the domain of chemical spectroscopy. Its implementation in this program is described in detail. .skip .begin nofill <<CS-712>> STAN-CS-79-712 @THE ERRATA OF COMPUTER PROGRAMMING Author: Donald E. Knuth 58 pages↔Cost: $3.35 .end @ABSTRACT: This report lists all corrections and changes of Volumes 1 and 3 of %2The Art of Computer Programming%1, as of January 5, 1979. This updates the previous list in report CS-551, May 1976. The second edition of Volume 2 has been delayed two years due to the fact that it was completely revised and put into the TEX typesetting language; since publication of this new edition is not far off, no changes to Volume 2 are listed here. .skip .begin nofill <<CS-713>> STAN-CS-79-713 @A HESSENBERG-SCHUR METHOD FOR THE PROBLEM AX + XB = C Authors: Gene Golub, Stephen Nash & Charles Van Loan 50 pages↔Microfiche only. .end @ABSTRACT: One of the most effective methods for solving the matrix equation AX + XB = C is the Bartels-Stewart algorithm. Key to this technique is the orthogonal reduction of A and B to triangular form using the QR algorithm for eigenvalues. A new method is proposed which differes from the Bartels-Stewart algorithm in that A is only reduced to Hessenberg form. The resulting algorithm is between 30 and 70 percent faster depending upon the dimensions of the matrices A and B. The stability of the new method is demonstrated through a roundoff error analysis and supported by numerical tests. Finally, it is shown how the techniques described can be applied and generalized to other matrix equation problems. .skip .begin nofill <<AIM-322>> AIM-322 @A FRAMEWORK FOR CONTROL IN PRODUCTION SYSTEMS Author: Michael Georgeff 35 pages↔Cost: $2.70 .end @Abstract: A formal model for representing control in production systems is defined. The formalism allows control to be directly specified independently of the conflict resolution scheme, and thus allows the issues of control and nondeterminism to be treated separately. Unlike previous approaches, it allows control to be examined within a uniform and consistent framework. @It is shown that the formalism provides a basis for implementing control constructs which, unlike existing schemes, retain all the properties desired of a knowledge based system --- modularity, flexibility, extensibility and explanatory capacity. Most importantly, it is shown that these properties are not a function of the lack of control constrains, but of the type of information allowed to establish these constraints. @Within the formalism it is also possible to provide a meaningful notion of the power of control constructs. This enables the types of control required in production systems to be examined and the capacity of various schemes to meet these requirements to be determined. @Schemes for improving system efficiency and resolving nondeterminism are examined, and devices for representing such meta-level knowledge are described. In particular, the objectification of control information is shown to provide a better paradigm for problem solving and for talking about problem solving. It is also shown that the notion of control provides a basis for a theory of transformation of production systems, and that this provides a uniform and consistent approach to problems involving subgoal protection. .skip .begin nofill <<CS-717>> STAN-CS-79-717 @ Authors: pages↔Cost: $ .end @Abstract: .skip .begin nofill <<AIM-323>> AIM-323 @AL USERS' MANUAL Authors: Shahid Mujtaba & Ron Goldman 136 pages↔Cost: $5.55 .end @Abstract: This document describes the current state of the AL system now in operation at the Stanford Artificial Intelligence Laboratory, and teaches the reader how to use it. The system consists of AL, a high-level programming language for manipulator control useful in industrial assembly research; POINTY, an interactive system for specifying representation of parts; and ALAID, an interactive debugger for AL. .skip .begin nofill <<CS-719>> STAN-CS-79-719 @EXTRAPOLATION OF ASYMPTOTIC EXPANSIONS BY A MODIFIED AITKEN %5d%1↑2-FORMULA Authors: Petter Bj%3O%1rstad, Germund Dahlquist & Eric Grosse 54 pages↔Microfiche only. .end @Abstract: A modified Aitken formula permits iterted extrapolations to efficiently estimate %5d%4↓∞%1 from %5d%2↓n%1 when an asymptotic expansion .skip .once center %5d%2↓n%2 = %5d%4↓∞%2 + n∩[-k](c↓0 + c↓1n∩[-1] + c↓2n∩[-2] + ...)%1 holds for some (unknown) coefficients %2c↓j%1. We study the truncation and irregular error and compare the method with other forms of extrapolation. .skip .begin nofill <<CS-720>> STAN-CS-79-720 @ON GRID OPTIMIZATION FOR BOUNDARY VALUE PROBLEMS Author: R. Glowinski 22 pages↔Microfiche only. .end @Abstract: We discuss in this report the numerical procedures which can be used to obtain the optimal grid when solving by a finite element method a model boundary value problem of elliptic type modelling the potential flow of an incompressible inviscid fluid. Results of numerical experiments are presented. .skip .begin nofill <<CS-721>> STAN-CS-79-721 @ON FAULT-TOLERANT NETWORKS FOR SORTING Authors: Andrew C. Yao & F. Frances Yao 20 pages↔Cost: $2.30 .end @Abstract: The study of constructing reliable systems from unreliable components goes back to the work of von Neumann, and of Moore and Shannon. The present paper studies the use of redundancy to enhance reliability for sorting and related networks build from unreliable comparators. Two models of fault-tolerant networks are discussed. The first model patterns after the concept of error-dorrecting codes in information theory, and the other follows the stochastic criterion used byvon Neumann and Moore-Shannon. It is shown, for example, that an additional k(2n-3) comparators are sufficient to render a sorting network reliable, provided that no more than k of its comparators may be faulty. .skip .begin nofill <<CS-722>> STAN-CS-79-722 @A STRUCTURAL MODEL FOR DATABASE SYSTEMS Authors: Gio Wiederhold & Ramez El-Masri 57 pages↔Cost: $3.30 .end @Abstract: A structural database model is presented. The model uses relations as building blocks of the data model, and classifies each relation into a structural type. This model can be considered as an extension of Codd's relational model [Codd70]. Both entities and associations among entities are represented as relations, and three further types of relations are introduced. A limited set of possible structural connections between the different types of relations is specified. The model, which was introduced informally by Wiederhold [Wiederhold77], implicityly defines a basic, limited set of integrity constraints. These integrity constraints identify existence dependencies among tuples from different relations. Rules for the maintenance of the structural integrity of the model under insertion and deletion of tuples are given. @A methodology for combining multiple, overlapping data models, or user views, is associated with the model. The database model, or conceptual schema, which represents the integrated database, may thus be derived from the individual data models of the users. We believe that the structural model could be used for representation of the data relationships within the conceptual schema of the ANSI/SPARC DBMS model since it can support database submodels (or external schema), and maintain the integrity of the submodels with respect to the integrity constraints expressable in the structural model. @We then briefly discuss the use of the structural model in database design and implementation. The structural model provides a tool to deal effectively with the complexity of large, real-world databases. .skip .begin nofill <<CS-723>> STAN-CS-79-723 @KNOWLEDGE ENGINEERING FOR MEDICAL DECISION MAKING: A REVIEW OF COMPUTER-BASED CLINICAL DECISION AIDS Authors: Edward Shortliffe, Bruce Buchanan & & Edward Feigenbaum 52 pages↔Cost: $3.20 .end @Abstract: Computer-based models of medical decision making account for a large proportion of clinical computing efforts. This article reviews representative examples from each of several major medical computing paradigms. These include (1) clinical algorithms, (2) clinical databanks that include analytic functions, (3) mathematical models of physical processes, (4) pattern recognition, (5) Bayesian statistics, (6) decision analysis, and (7) symbolic reasoning or artificial intelligence. Because the techniques used in the various systems cannot be examined exhaustively, the case studies in each category are used as a basis for studying general strengths and limitations. It is noted that no one method is best for all applications. However, emphasis is given to thelimitations of early work that have made artificial intelligence techniques and knowledge engineering research particularly attractive. We stress that considerable basic research in medical computing remains to bedone and that powerful new approaches may lie in the melding of two or more established techniques. .SKIP