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Research and Advances

A reply to gentleman and Marovich

Gentleman and Marovich in their short communication [Comm. ACM 17, 5 (May 1974) 276-277] make the claim that for FORTRAN “… the language definitions require that subprograms can be separately compiled…,” citing the ANSI FORTRAN standard X3.9-1966 as their authority.
Research and Advances

Matrix reduction—an efficient method

The paper describes an efficient method for reduction of the binary matrices which arise in some school time-tabling problems. It is a development of that described by John Lions. It has been generalized and adapted to fit into the complete timetabling process; to use a more compact data representation and more efficient processing techniques; to take fuller advantage of possible available previous knowledge about the matrix. And it is designed as a structured program, which can readily be coded by the reader in the high level or low level programming language of his choice. Practical tests of the method have shown it to be a good basis for a realistic timetabling algorithm.
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Research and Advances

A system for typesetting mathematics

This paper describes the design and implementation of a system for typesetting mathematics. The language has been designed to be easy to learn and to use by people (for example, secretaries and mathematical typists) who know neither mathematics nor typesetting. Experience indicates that the language can be learned in an hour or so, for it has few rules and fewer exceptions. For typical expressions, the size and font changes, positioning, line drawing, and the like necessary to print according to mathematical conventions are all done automatically. For example, the input sum from i=0 to infinity x sub i = pi over 2 produces ∑∞i=0xi = &pgr;/2 The syntax of the language is specified by a small context-free grammar; a compiler-compiler is used to make a compiler that translates this language into typesetting commands. Output may be produced on either a phototypesetter or on a terminal with forward and reverse half-line motions. The system interfaces directly with text formatting programs, so mixtures of text and mathematics may be handled simply. This paper was typeset by the authors using the system described.
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Research and Advances

On a solution to the cigarette smoker’s problem (without conditional statements)

This report discusses a problem first introduced by Patil, who has claimed that the cigarette smoker's problem cannot be solved using the P and V operations introduced by Dijkstra unless conditional statements are used. An examination of Patil's proof shows that he has established this claim only under strong restrictions on the use of P and V. These restrictions eliminate programming techniques used by Dijkstra and others since the first introduction of the semaphore concept. This paper contains a solution to the problem. It also discusses the need for the generalized operators suggested by Patil.
Research and Advances

Glypnir—a programming language for Illiac IV

GLYPNIR is one of the earliest existing languages designed for programming the Illiac IV computer. The syntax of the language is based on ALGOL 60, but has been extended to allow the programmer explicitly to specify the parallelism of his algorithm in terms of 64-word vectors. This paper describes the characteristics, goals, and philosophy of the language, and discusses some of the problems associated with parallel computer architectures.
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Research and Advances

Sentence paraphrasing from a conceptual base

A model of natural language generation based on an underlying language-free representation of meaning is described. A program based on this model is able to produce sentence paraphrases which demonstrate understanding with respect to a given context. This generator operates in conjunction with a natural language analyzer and a combined memory and inference model. In generating sentences from meaning structures, the program employs both the information retrieval and deduction capabilities of the memory model. The model encompasses several diverse classes of linguistic knowledge, which include: (1) executable tests of conceptual properties stored in discrimination nets; (2) information relating conceptual to syntactic roles, stored in a word-sense dictionary, and (3) surface grammatical knowledge, stored in a formal grammar.
Research and Advances

Anaysis of interleaved memory systems using blockage buffers

A model of interleaved memory systems is presented, and the analysis of the model by Monte Carlo simulation is discussed. The simulations investigate the performance of various system structures, i.e. schemes for sending instruction and data requests to the memory system. Performance is measured by determining the distribution of the number of memory modules in operation during a memory cycle. An important observation from these investigations is that separately grouping instruction and data requests for memory can substantially increase the average number of memory modules in operation during a memory cycle. Results of the simulations and an analytical study are displayed for various system structures.
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Research and Advances

State-space problem-reduction, and theorem proving—some relationships

This paper suggests a bidirectional relationship between state-space and problem-reduction representations. It presents a formalism based on multiple-input and multiple-output operators which provides a basis for viewing the two types of representations in this manner. A representation of the language recognition problem which is based on the Cocke parsing algorithm is used as an illustration. A method for representing problems in first-order logic in such a way that the inference system employed by a resolution-based theorem prover determines whether the set of clauses is interpreted in the state-space mode or in the problem-reduction mode is presented. The analogous concepts in problem-reduction and theorem proving, and the terminology used to refer to them, are noted. The relationship between problem-reduction, input resolution, and linear resolution is is discussed.
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Research and Advances

Professionalism in the computing field

The term professional means different things to different people; nevertheless, there are certain general technical and social standards normally associated with a professional. Further, the term is more generally applied to the practitioner rather than to the researcher. But within the rather broad definition specified, the computing practitioner is, as yet, not regarded as a professional. Each of the four types of institutions—academic, industry, government, and the professional society—that educate, employ, regulate, and mold the practitioner contributes to the “nonprofessional” status of the computing practitioner. The roles of these institutions are examined, various shortcomings are noted, and recommended changes are suggested. In the last analysis, professional status is not bestowed; it is earned. However, universities and industry, specifically, can make certain improvements to help the computing practitioner achieve professional status.
Research and Advances

The new math of computer programming

Structured programming has proved to be an important methodology for systematic program design and development. Structured programs are identified as compound function expressions in the algebra of functions. The algebraic properties of these function expressions permit the reformulation (expansion as well as reduction) of a nested subexpression independently of its environment, thus modeling what is known as stepwise program refinement as well as program execution. Finally, structured programming is characterized in terms of the selection and solution of certain elementary equations defined in the algebra of functions. These solutions can be given in general formulas, each involving a single parameter, which display the entire freedom available in creating correct structured programs.
Research and Advances

Storage-efficient representation of decimal data

Usually n decimal digits are represented by 4n bits in computers. Actually, two BCD digits can be compressed optimally and reversibly into 7 bits, and three digits into 10 bits, by a very simple algorithm based on the fixed-length combination of two variable field-length encodings. In over half of the cases the compressed code results from the conventional BCD code by simple removal of redundant 0 bits. A long decimal message can be subdivided into three-digit blocks, and separately compressed; the result differs from the asymptotic minimum length by only 0.34 percent. The hardware requirement is small, and the mappings can be done manually.
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Research and Advances

Computer programming as an art

When Communications of the ACM began publication in 1959, the members of ACM's Editorial Board made the following remark as they described the purposes of ACM's periodicals [2]: “If computer programming is to become an important part of computer research and development, a transition of programming from an art to a disciplined science must be effected.” Such a goal has been a continually recurring theme during the ensuing years; for example, we read in 1970 of the “first steps toward transforming the art of programming into a science” [26]. Meanwhile we have actually succeeded in making our discipline a science, and in a remarkably simple way: merely by deciding to call it “computer science.”
Research and Advances

A heuristic approach to inductive inference in fact retrieval systems

Heuristic procedures are presented which have been developed to perform inferences by generalizing from available information. The procedures make use of a similarity structure which is imposed on the data base using nonnumerical clustering algorithms. They are implemented in a model fact retrieval system which uses a formal query language and a property-list data structure. A program of experiments is described wherein the procedures are used with test data bases which are altered by deleting part of the data and by purposely introducing false data. It is found that the system can infer the correct response under a variety of conditions involving incomplete and inconsistent data.

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