Conference report12th IEEE international symposium onmultiple-valued logic (MVL 82)

CNAM, Paris, 24th-27th May 1982

This symposium, the twelfth in this annual event, and thesecond held outside North America, was held in the historicalsurroundings of the Conservatoire National des Arts et Metiers(CNAM) in Paris, under the joint sponsorship of the IEEEComputer Society, the IEEE Multiple Valued Logic TechnicalCommittee, the Institut de Programmation de l'Universite,Paris, the Centre National de la Recherche Scientifique, andCNAM. The pattern of the symposium and the range of paperspresented followed well established practice, although thenumber of contributions this year necessitated more parallelsessions being held than has been customary in the past.

The subject areas of (i) fundamental algebraic considerations,(ii) fuzzy logic and implications, (iii) number representationsfor radices greater than two, (iv) multiple-valued networksynthesis and testing, and (v) multiple-valued circuit realisation,were all represented during the three days of the conference.A number of papers of particular significance and interest werepresented.

Algebraic considerations of many-valued logic were coveredby a number of authors, including, for the first time in MVLsymposia, presentations from Eastern European authors. Twocomplementary contributions in this area, given by J. Henno(Tallinn Polytechnic Institute, Tallinn, USSR) and by R.Balramov (Aberbaijan Academy of Sciences, Baku, USSR),may be cited. The former considered equivalent sets of func-tions of multiple-valued logic, developing appropriate algebraicrelationships to define equivalence, whereas the latter con-sidered independent sets of functions in finite-valued algebras.Further contributors considered other algebraic aspects, in-cluding a paper by J. Demetrovics and L. Hannak (HungarianAcademy of Sciences, Budapest) on the number of functionallycomplete algebras.

An interesting development in this 1982 symposium wasthe application of the mathematics of multiple-valued logicand fuzzy logic to philosophic areas and social decision mech-anisms. A paper by T. Kitahashi (Toyohashi University ofTechnology, Japan) entitled 'Social decision and ternarymajority functions' modelled the decision logic of representa-tive systems, such as parliaments and proportional represen-tation, by the use of ternary majority functions. The majoritydecision principle discussed permitted abstention and weightedvotes in the final threshold decision output, together withhierarchical decision tree structures. A further paper byS.V. Ovchinnikov (University of California, Berkeley) entitled'Social choice and Lukasiewicz logic' addressed a similar areaof social choice theory. However, to match these philosophicareas, very little was presented in the area of engineeringdecisions and systems operating with unquantised input data.

Number representations for systems with a radix greaterthan two (binary) received a noticeable degree of attention inthe previous 1981 MVL symposium, and, as a result, possiblywere not so prominent in the current year's proceedings.However, reinforcement of the advantages gained by the useof higher-valued radix was made in several contributions; inparticular, the mathematical advantages of radix-four signed-

digit system were detailed, among the advantages being thatthe carry propagation is always limited to one bit to the left,and that sign conversion from positive to negative numbers isvery straightforward.

The synthesis of multiple-valued logic systems remains anarea.ofdifficultyifadesign optimised in some sense is required.A paper by W. S. Wojciechowski entitled 'Structured digitalsystems design in multiple-valued logic' treated the subject ina simple structured manner, the final realisation being in theform of multiple-valued multiplexer elements (T-gates) andD-type flip-flops. Although the procedure discussed has a veryappealing design strategy, optimality of design by consideringthe effect of the choice of the data select inputs to the T-gateswas not considered. Testing of multiple-valued logic networkswas considered in a paper by D.M. Miller, presented in hisabsence by J.C. Muzio, the method presented being the general-isation of a spectral technique from the binary case to themore general multiple-valued case. The procedure discussedinvolved the formulation of a subset of spectral coefficientvalues which would provide a minimum test set for the net-work under test, with a forward look to the possibilities ofdesigning a network for ease of testability.

A final comment must be made upon a strong divergence ofopinion which emerged in MVL 82, as to the future trends inmultiple-valued logic systems. Given (a) the vast investmentin binary systems and expertise, but also (b) the increasingpressure on limiting the number of interconnect lines andI/O ports, two schools of thought may be observed. The firststates that the main interconnect highways shall carry multiple-valued logic signals, with I/O decoders translating the higher-valued signals to or from binary; the central hardware circuitsof the system shall remain binary, to capitalise upon theexpertise now available in the design of binary logic systems.The alternative school of thought states that the advantages ofhigher-valued logic working, particularly for high-speed com-putational problems, are so considerable that the centralhardware circuits will become multiple valued, with decodingfrom multiple valued to binary, so as to interface with the vastrange of binary-operated peripherals which are currentlyavailable. The future advent, however, of truly multiple-valueddevices, such as opto-electronic devices, from which to assemblethe hardware systems, would play a dominant part in the out-come of this dichotomy.

The symposium Proceedings are obtainable from the IEEEComputer Society, PO Box 80452, Worldway Postal Center,Los Angeles, CA 90080, USA, the IEEE catalogue numberbeing 82CH 1757-4.

In 1983, the MVL symposium will be held in Kyoto, Japan,during the period 23rd—25th May, and in 1984 will return toNorth America, where it will be held in Canada at the Uni-versity of Manitoba, Winnipeg. Information on die 1983symposium may be obtained from Professor T. Kitahashi,Symposium Chairman ISMVL 83, School of Information andComputer Sciences, Toyohashi University of Technology,Toyohashi, Japan 440.

S.L. HURST

216 IEEPROC, Vol. 129, Pt. E, No. 5, SEPTEMBER 1982