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Research and Advances Dec 1 1982

On the emulation of flowcharts by decision tables

Any flowchart can be emulated by a decision table, whose complexity depends on that of the flowchart. It may be necessary, however, to introduce a new control variable with associated tests and sets or to permit changes in execution sequences provided action-test independence holds. Two measures of decision table complexity are discussed and interrelated. Finally, conditions and procedures for reducing complexity are presented.
Research and Advances Dec 1 1982

A hash code method for detecting and correcting spelling errors

The most common spelling errors are one extra letter, one missing letter, one wrong letter, or the transposition of two letters. Deletion, exchange, and rotation operators are defined which detect and “mend” such spelling errors and thus permit retrieval despite the errors. These three operators essentially delete a letter of a word, exchange two adjacent letters, and rotate a word cyclically. Moreover, the operators can be used in conjunction with hashing, thus permitting very fast retrieval. Results of experiments run on large databases in Hebrew and in English are briefly indicated.
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Opinion Dec 1 1982

ACM forum

This is a comment on “File Archival Techniques Using Data Compression” by Michael Pechura [Communications, Sept. 1982, p. 605]. We approached the data compression problem with the aim of maximizing the saving in archival storage over all files for which archival storage was necessary. We also wanted a routine which was reasonably economic in use of system resource.
Research and Advances Dec 1 1982

A critique of the foundations of Hoare style programming logics

Much recent discussion in computing journals has been devoted to arguments about the feasibility and usefulness of formal verification methods. Too little attention has been given to precise criticism of specific proposed systems for reasoning about programs. Whether such systems are to be used for formal verification, by hand or automatically, or as a rigorous foundation for informal reasoning, it is essential that they be logically sound. Several popular rules in the Hoare language are, in fact, not sound. These rules have been accepted because they have not been subjected to sufficiently strong standards of correctness. This paper attempts to clarify the different technical definitions of correctness of a logic, to show that only the strongest of these definitions is acceptable for Hoare logic, and to correct some of the unsound rules that have appeared in the literature. The corrected rules are given merely to show that it is possible to do so. Convenient and elegant rules for reasoning about certain programming constructs will probably require a more flexible notation than Hoare's.
Research and Advances Dec 1 1982

An effective way to represent quadtrees

A quadtree may be represented without pointers by encoding each black node with a quaternary integer whose digits reflect successive quadrant subdivisions. We refer to the sorted array of black nodes as the “linear quadtree” and show that it introduces a saving of at least 66 percent of the computer storage required by regular quadtrees. Some algorithms using linear quadtrees are presented, namely, (i) encoding a pixel from a 2n × 2>n array (or screen) into its quaternary code; (ii) finding adjacent nodes; (iii) determining the color of a node; (iv) superposing two images. It is shown that algorithms (i)-(iii) can be executed in logarithmic time, while superposition can be carried out in linear time with respect to the total number of black nodes. The paper also shows that the dynamic capability of a quadtree can be effectively simulated.
Research and Advances Dec 1 1982

Implementations for coalesced hashing

The coalesced hashing method is one of the faster searching methods known today. This paper is a practical study of coalesced hashing for use by those who intend to implement or further study the algorithm. Techniques are developed for tuning an important parameter that relates the sizes of the address region and the cellar in order to optimize the average running times of different implementations. A value for the parameter is reported that works well in most cases. Detailed graphs explain how the parameter can be tuned further to meet specific needs. The resulting tuned algorithm outperforms several well-known methods including standard coalesced hashing, separate (or direct) chaining, linear probing, and double hashing. A variety of related methods are also analyzed including deletion algorithms, a new and improved insertion strategy called varied-insertion, and applications to external searching on secondary storage devices.
Research and Advances Nov 1 1982

HISDL—a structure description language

The features of a language designed for the description of the structure of computer systems are described. The structure of a system is specified hierarchically as an interconnection of components with each component being a named instance of a component type. The system itself is another component type. The interconnection between components is specified in two ways: either by specifying all the ports that are connected together, or by specifying a component and the ports that are connected to its ports. A structure specification is a list of such connection specifications. The language has an iterative construct for specifying highly regular structures, and a conditional construct is also provided. A component type can be recursively specified while parameterization of component type specifications is supported. The latter is particularly useful for specifying classes of components of similar structure.
Research and Advances Nov 1 1982

The impact of office automation on the organization: some implications for research and practice

Computer technology has recently been applied to the automation of office tasks and procedures. Much of the technology is aimed not at improving the efficiency of current office procedures, but at altering the nature of office work altogether. The development of automated office systems raises a number of issues for the organization. How will this technology be received by organization members? How will it affect the definition of traditional office work? What will be its impact on individuals, work groups, and the structure of the organization? This paper presents a descriptive model and propositions concerning the potential impacts of office automation on the organization and it stresses the need, when implementing automated office systems, to take a broad perspective of their potential positive and negative effects on the organization. The need for further research examining the potential effects of office automation is emphasized.
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Research and Advances Nov 1 1982

The distribution of granule accesses made by database transactions

The problem of characterizing the number of granules (or blocks) accessed by a transaction is important in modeling the performance of database management systems and other applications. Different expressions for this quantity have appeared in the literature under different probabilistic assumptions. These expressions along with one new result are presented with a uniform notation and a clear statement of the assumptions underlying each. The partial order relating the predictions of the expected number of granules accessed is presented.
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Research and Advances Nov 1 1982

MINI-EXEC: a portable executive for 8-bit microcomputers

As microprocessor systems and single-chip microcomputers become more complex, so do the software systems developed for them. In many cases, software is being designed that incorporates multiple control functions running asynchronously on a single microprocessor. Here, discussion focuses on the motivation for running such multiple functions under the control of a real-time multitasking executive. A successfully implemented executive whose design is portable and suitable for use on most 8-bit microprocessors is presented.
Research and Advances Nov 1 1982

Unionization of professionals in data processing: an assessment of recent trends

The needs of management, unions, employees, and computer professionals combined with existing practices of Labor Relations Boards and the various divisions in the Departments of Labor have combined to create a unique array of social conflicts. At the root are management's interest in keeping many skills in data processing and computing out of bargaining units and the union's interest in including as many of these skills as possible. There is also conflict between past strategies guiding labor relations and the structure and function of professional work in modern organizations. Two recent developments are analyzed: (1) The FAA's success in keeping airports operational with the help of computer-controlled air flow procedures; (2) Management's successful bids to exclude professional engineers working in data processing jobs from bargaining units. At the same time, the National Labor and Mediation Boards have rejected attempts to define data processing jobs including highly skilled systems analysts as a separate craft or class for representation purposes while granting such status to engineers in similar employment situations. If this principle of exclusion from unions of licensed and certified professionals who are doing DP work is established in North America, it may lead to increased labor unrest in many highly automated and data processing industries.
Research and Advances Nov 1 1982

Information systems curriculum recommendations for the 80s: undergraduate and graduate programs

The recommendations of the 1972 and 1973 ACM Curriculum Committee on Information Systems programs have been influential in the development of degree programs at the bachelor's, master's, and doctoral levels. The earlier curriculum has been revised and updated based on advances in the field over the past nine years. The report discusses the continuing need for education related to the definition, analysis, design, construction, and management of information systems in organizations. The structure of both bachelor's and master's level programs are described and courses are defined. Course outlines include rationale for the courase, course objectives, instructional modes, and a list of topics. Each topic is weighted in terms of suggested percent of time devoted to the subject.
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