Lecture Not ens i Computer Science Edited by G. Goos and .J Hartmanis 17 IIIIIIIII IIIIII II III I II I I I I III I I I ,atamotuA segaugnaL dna gnimmargorP Colloquium, Sixth Graz, July Austria, 16-20, 1979 Edited yb Hermann .A Maurer I IIII IIII I II II I galreV-regnirpS nilreB Heidelberg kroYweN 1979 Editorial Board P. Brinch Hansen D. Gries C. Moler G. Seegm~iller .J Stoer N. Wirth Editor Hermann A. Maurer Institut f0r Informations- verarbeitung Technische Universit~it Graz Steyrergasse 17 8010 Graz/Austria AMS (1970): Subject Classifications 68-XX CR Subject (1974): 4.1, Classifications 4.2, 5.2, 5.3 tSBN 3-540-09510-1 Berlin Heidelberg Springer-Verlag New York ISBN 0-387-09510-1 Springer-Verlag New York Heidelberg Berlin Library of Congress Cataloging in Publication Data. Colloquium on Automata, Languages and programming, 6th, Graz, 1979. Automata, languages and programming.( Lecture notes in computer science ; )17 Includes index. .1 Sequential machinteh eory--Congresses. 2. Formal languages--Congresses, 3. Programming languages (Electronic computers)--Congresses. .I Maurer, Hermann 1941- A., .II Title. LlI Series. QA267.5S4C63 1979 001.6'42 ?~-15859 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned,s pecifically thoseo f translationr,e printing, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under § 54 of the Germa n Copyright Law where copies are made for other than private use, a fee is payable to the publisher, the amount of thef ee to be determined by agreement with the publisher. @ by Springer-Verlag Berlin Heidelberg 1979 Printed in Germany Printing and binding: BeltOzf fsetdruck, Hemsbach/Bergstr. 2145/3140-543210 ECAFERP ehT Sixth Colloquium no Automata, segaugnaL dna gnimmargorP (ICALP )97 saw dedecerp by similar colloquia in Paris (1972), SaarbrUcken (1974), Edinburgh (1976), Turku (1977) dna Udine (1978), all sponsored by SCTAE (European Association for Theoretical retupmoC Science). Of a total of 931 papers submitted to PLACI 79, fifty papers were selected. Together with three invited presentations they are contained in this volume. ehT program committee of PLACI 97 consisted of G.Ausiello, W.Brauer, K.Culik II, J. ed Bakker, E.Engeler, S.Even, M.Harrison, l.M.Havel, J.Hopcroft, G.Hotz, W.Kuich, H.Maurer (chairman), M.Nivat, M.Paterson, Z.Pawlak, A.Salomaa, ,dooW.D H.Zima. sA conference chairman, I would like to thank the srebmem of the program committee for their hard work in evaluating the submitted papers. Special thanks are also eud to the following referees ohw helped in the refereeing process: A.Aho, J.Albert, .G Andrews, K.R.Apt, J.Archer, E.A.Ashcroft, L.Banachowski, G.Baron, C.Batini, J.C.Beatty, J.Becvar, D.Bini, A.Blikle, ,mh~B.C R.Book, S,Breidbart, .A ed Bruin, J.Brzozowski, R.Cartwright, L.M.Chirica, R.S.Cohen, A.B.Cremers, P.Dembinski, K.Ecker, H.Ehrig, .M Furst, G.Gati, G.Goos, J.Gorski, M.Grabowski, D.Gries, J.Gruska, J.Grzymala-Busse, .V Haase, M.Hofri, M.Jazayeri, J.Karhum~ki, O.Kariv, M.Karpinski, C.Keleman, B.Konilcowska, A.Krecmar, H.P.Kriegel, F.Krieger, M.Lao, R.Leip~l~, M.Linna, F.Luk, G.Mahr, T.S.E. ,muabiaM J.Maluszynski, A.Marchetti-Spaccamela, A.Mazurkiewicz, L.G.L.T.Meertens, .R Milner, A.Moura, T.MUldner, K.MUIIer, E.J.Neuhold, A.Ob~tulowicz, J.Opatrny, Th.Ott- ,nnam D.M.R.Park, A.Paz, M.Penttonen, A.Pettorossi, F.PIAsil, H.Prodinger, V.Rajlich, P.Raulefs, J.C.Reynolds, J.L.Richier, ,hedoR.M edLP.W Roever,'F.Romani, D.Rotem, .P Ruzicka, A.Salwicki, G.Schlageter, F.Schneider, E.Shamir, J.Simon, M.Steinby, W.Stucky, S.Termini, J.W.Thatcher, F.J.Urbanek, V.K.Vaishnavi, P.van edmE Boas, J.van ,newueeL J.Weglarz, L.Wegner, K.Weihrauch, J.Winkowski, C.K.Yap. Finally, the support of the Austrian Federal Ministry for Science dna Research, the Province of Styria, the City of Graz, the Center Research Graz, MBI Austria, Sperry Univac, the Institut f. etdnawegnA Informatik dnu Formale Beschreibungsverfahren - Universit~t Karlsruhe dna the Technical University of Graz is gratefully .degdelwonkca Last not least, I want to thank the srebmem of the organizing committee dna ym secre- tary Mrs. A.Kleinschuster for their help in organizing the conference, dna Springer- Verlag for excellent cooperation concerning the publication of this volume. Graz, April 9791 nnamreH Maurer STNETNOC E.Astesiano and G.Costa Sharing in nondeterminism . . . . . . . . . . . . . . . . . J.Berstel Sur les mots sans carr~ d~finis par un morphisme . . . . . . . . . 61 A.Bertoni, G.Mauri and P.A.Miglioli A characterization of abstract data as model-theoretic invariants 26 M.Blattner Inherent ambiguities in families of grammars . . . . . . . . . . 38 R.V.Book and F.-J.Brandenburg Representing complexity classes by equality sets . . . . . . . . . 49 B.v.BraunmUhl and E.Hotzel Supercounter machines . . . . . . . . . . . . . . . . . . 58 M.Broy, W.Dosch, H.Partsch, P.Pepper and M.Wirsing Existential quantifiers in abstract data types . . . . . . . . . . 37 C.Choffrut A generalization of Ginsburg and Rose's characterization of G-S-H mappings . . . . . . . . . . . . . . 88 L.Chottin Strict deterministic languages and controlled rewriting systems . . . . 401 B.Commentz-Walter A string matching algorithm fast on the average . . . . . . . . . 118 M.Coppo, M.Dezani-Ciancaglini and .P Salle' Functional characterization of some semantic equalities inside ~-calculus . . . . . . . . . . . . . 133 Vl A.B.Cremers and T.N.Hibbard Arbitration and queueing under limited shared storage requirements . . . . 741 K.Culik II nO the homomorphic characterizations of families of languages . . . . . . 161 P.Dembihski and J.Ma~uszyhski owT level grammars: CF-grammars with equation schemes . . . . . . . . . 171 N.Dershowitz and Z.Manna Proving termination with multiset orderings . . . . . . . . . . . . 188 P.Deussen enO abstract accepting algorithm for all kinds of parsers . . . . . . . . 203 A.G.Duncan and L.Yelowitz Studies in abstract/concrete mappings in proving algorithm correctness 218 F.E.Fich and J.A.Brzozowski A characterization of a dot-depth two analogue of generalized definite languages . . . . . . . . . . . . . . . . 230 D.Friede Partitioned LL(k) grammars . . . . . . . . . . . . . . . . . . 245 J.H.Gallier Recursion schemes and generalized interpretations . . . . . . . . . . 256 J.Goldstine A rational theory of AFLs . . . . . . . . . . . . . . . . . . 271 J.Hartmanis nO the succinctness of different representations of languages . . . . . . 282 S.Istrail A fixed-point theorem for recursive-enumerable languages and some considerations about fixed-point semantics of monadic programs . . . . 289 IIV oknaJ.W Hierarchic index sequential search with optimal variable block size dna its minimal expected rebmun of comparisions . . . . . . . . . 403 dnornaeJ.J,H A unique termination theorem for a theory with generalised commutative axioms . . . . . . . . . . . . . . . . 613 arumimaK.T dna G.Slutzki Dags and Chomsky hierarchy . . . . . . . . . . . . . . . . . 331 R.Karp Recent advances in the probabilistic analysis of graph-theoretic algorithms (Invited address) . . . . . . . . . . . 338 pmeK.R nO the average stack size of regularly distributed binary trees . . . . . 340 W.Kowalk and R.Valk nO reductions of parallel programs . . . . . . . . . . . . . . . 356 W.Kuich, H.Prodinger and F.J.Urbanek nO the height of derivation trees . . . . . . . . . . . . . . . 370 Z.Manna and A.Pnueli The modal logic of programs (Invited address) . . . . . . . . . . . 385 F.Meyer auf der Heide A comparision between two variations of a pebble game on graphs . . . . . 411 D.R.Milton and C.N.Fischer LL(k) parsing for attributed grammars . . . . . . . . . . . . . . 422 B.Monien and l.H.Sudborough nO eliminating nondeterminism from Turing machines which use less than logarithm worktape space . . . . . . . . . . . 431 VIII A.Nijholt Structure preserving transformations no non-left-recursive grammars . . . . 644 C.H.Papadimitriou dna M.Yannakakis ehT complexity of restricted muminim spanning tree problems . . . . . . . 064 grebnezoR.G A systematic approach to formal language theory through parallel rewriting (Invited address) . . . . . . . . . . . . 174 grebnezoR.G dna D.Vermeir Extending the notion of finite index . . . . . . . . . . . . . . 974 ozzuR.L.W nO the complexity of general context-free language parsing dna recognition . . . . . . . . . . . . . . . . . . 984 J.E.Savage dna ymawS.S Space-time tradeoffs for oblivious integer multiplication . . . . . . . 894 tdimhcS.G Investigating programs in terms of partial graphs . . . . . . . . . . 505 egahn~hcS.A nO the power of modnar access machines . . . . . . . . . . . . . 025 R.L.Schwartz nA axiomatic treatment of LOGLA 86 routines . . . . . . . . . . . . 035 namleS.L.A P-selective sets, tally languages, dna the behavior of polynomial time reducibilities no PN . . . . . . . . . . . . . 645 R.Sethi dna gnaT,A Constructing call-by-value continuation semantics . . . . . . . . . . 655 sdleihS.W.M dna P,E.Lauer A formal semantics for concurrent systems . . . . . . . . . . . . . 175 XJ S.Sippu and E.Soisalon-Soln,..en nO constructing LL(k) parsers . . . . . . . . . . . . . . . . . 585 J.W.Thatcher. E.G.Wagner and J.B.Wright More on advice on structuring compilers and proving them correct . . . . . 695 D.Th~rien Languages of nilpotent and solvable groups . . . . . . . . . . . . 616 J .Tiuryn Unique fixed points vs. least fixed points . . . . . . . . . . . . 633 E, Ukkonen A modification of the LR(k) method for constructing compact bottom-up parsers . . . . . . . . . . . . . . . . . . 646 k,Ury Optimal decomposition of linear automata . . . . . . . . . . . . . 659 .Wegner L Bracketed two-level grammars - a decidable and practical approach to language definitions . . . . . . . . . . . . 668 Index of authors . . . . . . . . . . . . . . . . . . . 683 SHARING IN NONDETERMINISM Egidio ASTESIANO - Gerardo COSTA Istituto di Matematica dell'Universitg di Genova Via L.B.Alberti, 4 - 16132 Genova - Italy ABSTRACT. We consider a language of typed ~-expressions with primitives including nondeterministic choice operators. Starting from the natural idea that a ~irst order nondeterministic procedure should define a one-many function, we give a reduction system in which ground arguments are shared, in order to avoid some unnatural conse- quences due to unrestricted application of the copy-rule. This is achieved by extending the language and modifying the usual ~-rule. Then we discuss how to define a correspo~ ding denotational semantics, establishing in particular the existence of a model which is fully abstract w.r.t, the operational semantics. .] INTRODUCTION Consider the usual language of first order deterministic recursive vrocedures, enriched with a binary choice operator or and extend the usual evaluation mechanism by letting t or 't evaluate to either t or 't . Then consider the following exam- ple /HA1/ ~ where x ranges over the domain of non-negative integers ~ : F(x) ~= if x=O then O else G(x or x-l) G(x) #= if x=O then O else if x=l then I else 2 Evaluation of F(1), using an outermost strategy, yields, as possible values, O, I and 2. Hennessy and Ashcroft point out that in a functional model corresponding to this evaluation strategy F and G cannot denote functions f and g from ~ into ~ . 2 Indeed we would have: f(1) = g({O,l}) = g(O) U g(1) = {O,I} , in contrast with the operational result. This motivates in /HAI,HA2/ the choice of a model in which the meanings for F and G are functions from ~ \ 2 {@} into itself. From a mathematical point of view, how- ever, it seems perfectly reasonable to take a different apvroaeh: the equation for G is deterministic and by itself defines a function from ~ into ~ , it should then defi- ne the "same" (see below) function when considered together with the equation for F. In general, it is mathematically sound to say that nondeterministic recursive proce- dures define one-many functions. In this framework, deterministic procedures, like the one for G, define one-singleton functions and the result of a~plying a function f to a set A is given by U {f(a), @ a A} . This is the approach we shall take here (the same choice is made in /ANI,A~N2/, though in a different setting). Looking for an operational semantics corresponding to this (intuitive) model, we remark that the point in the above example is that G makes two copies of its argument,