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Research and Advances Jun 1 1974

An information-theoretic approach to text searching in direct access systems

Using direct access computer files of bibliographic information, an attempt is made to overcome one of the problems often associated with information retrieval, namely, the maintenance and use of large dictionaries, the greater part of which is used only infrequently. A novel method is presented, which maps the hyperbolic frequency distribution of text characteristics onto a rectangular distribution. This is more suited to implementation on storage devices. This method treats text as a string of characters rather than words bounded by spaces, and chooses subsets of strings such that their frequencies of occurrence are more even than those of word types. The members of this subset are then used as index keys for retrieval. The rectangular distribution of key frequencies results in a much simplified file organization and promises considerable cost advantages.
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Research and Advances Mar 1 1974

Emotional content considered dangerous

I had hoped that Moorer's rebuttal to my short communication in the November 1972 Communications would close the debate on a topic which, like the computer itself, has provoked an inordinately large quantity of unqualified argument. Unfortunately, the short communications by McMorrow and Wexelblat in the May 1973 Communications lead me to believe that my position is still grossly misunderstood. Therefore, allow me to clarify these matters.
Research and Advances Mar 1 1974

Scan conversion algorithms for a cell organized raster display

Raster scan computer graphics with “real time” character generators have previously been limited to alphanumeric characters. A display has been described which extends the capabilities of this organization to include general graphics. Two fundamentally different scan conversion algorithms which have been developed to support this display are presented. One is most suitable to noninteractive applications and the other to interactive applications. The algorithms were implemented in Fortran on the CDC6400 computer. Results obtained from the implementations show that the noninteractive algorithms can significantly reduce display file storage requirements at little cost in execution time over that of a conventional raster display. The interactive algorithm can improve response time and reduce storage requirements.
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Research and Advances Feb 1 1974

Attribute based file organization in a paged memory environment

The high cost of page accessing implies a need for for more careful data organization in a paged memory than is typical of most inverted file and similar approaches to multi-key retrieval. This article analyses that cost and proposes a method called multiple key hashing which attempts to minimize it. Since this approach is not always preferable to inversion, a combined method is described. The exact specifications of this combination for a file with given data and traffic characteristics is formulated as a mathematical program. The proposed heuristic solution to this program can often improve on a simple inversion technique by a factor of 2 or 3.
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Research and Advances Nov 1 1969

Synchronization in a parallel-accessed data base

The following problem is considered: Given a data base which can be manipulated simultaneously by more than one process, what are the rules for synchronization which will maximize the amount of parallel activity allowed. It is assumed that the data base can be represented as a graph. An example of such a data base is a hierarchy of directories for an on-line file system. Methods for synchronization of processes are examined; their validity is discussed and their performance compared.
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Research and Advances Nov 1 1969

An interactive graphical display monitor in a batch-processing environment with remote entry

A graphic monitor program is described. It was developed at Carnegie-Mellon University for the CDC G21 computer, which is a general purpose, batch-processing system with remote entry. The existing G21 system and the graphics hardware are described. The graphic monitor is a resident auxiliary monitor which provides comprehensive managerial capability over the graphical system in response to commands from the human user. It also will respond to commands from a user program through a similar interface, where routine calls take the place of manual actions. Thus the human and program can interact on a symmetrical and equal basis through the medium of the graphic monitor. The choices made in designing the graphic monitor, given the constraints of the existing hardware and computer system, are discussed. The structure of the monitor program and the human and program interfaces are described. There is also a transient swapping version with a small resident part, and provision for swapped used submonitors.
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Research and Advances Oct 1 1969

A comment on optimal tree structures

In Y.N. Patt's paper “Variable Length Tree Structures Having Minimum Average Search Time” [Comm. ACM 12 (Feb. 1969)], the tree structures obtained are not actually optimal with respect to the two-dimensional chaining devised by Sussenguth in his 1963 paper. This note points out that the result can be described as “optimal” only under the constraint—which Patt implicity assumes—that no key be allowed to prefix another.
Research and Advances May 1 1969

Time-sharing and batch-processing: an experimental comparison of their values in a problem-solving situation

An experimental comparison of problem-solving using time-sharing and batch-processing computer systems conducted at MIT is described in this paper. This study is the first known attempt to evaluate two such systems for what may well be the predominant user population within the next decade—the professionals who, as nonprogrammers, are using the computer as an aid in decision-making and problem-solving rather than as a programming end in itself. Statistically and logically significant results indicate equal cost for usage of the two computer systems; however, a much higher level of performance is attained by time-sharing users. There are indications that significantly lower costs would have resulted if the time-sharing users had stopped work when they reached a performance level equal to that of the batch users. The users' speed of problem-solving and their attitudes made time-sharing the more favorable system.
Research and Advances Mar 1 1969

Concepts of use in contour map processing

Generalized techniques are developed whose use can simplify the solution of problems relating to contour maps. One of these techniques makes use of the topological properties of contour maps. The topology is represented by a graphical structure in which adjacent contour lines appear as connected nodes. Another generalized technique consists of utilizing geometrical properties to determine the characteristics of straight lines drawn on the contour map. Both of these techniques have been applied to the problem of locating the ground track of an aircraft from elevation readings obtained during a flight.
Research and Advances Feb 1 1969

CODAS: a data display system

CODAS, a Customer Oriented Data System, is a user-oriented data retrieval and display system. The command language of the system provides the user with an easy means for specifying data retrieval and display requests. Data is displayed as tables and graphs produced in a format ready for publication. In this paper the statements of the request language and the general system design are described.
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Research and Advances Dec 1 1967

The LACONIQ monitor: time sharing for online dialogues

The LACONIQ (Laboratory Computer Online Inquiry) Monitor was developed primarily to support non-numerical applications such as retrieval from very large files by means of a “dialogue” between a system user and a retrieval application. The monitor was designed so that it could work with a small computer (an IBM System 360/30). Therefore techniques for resource allocation were important. For this reason the use of core storage, computational facilities, and input-output were all scheduled. An unusual feature of the system is that it is event-driven rather than clock-driven. The program segments called into execution by the remote CRT consoles are invariably run to completion rather than “rolled-out” to be brought back at a later time.
Research and Advances Nov 1 1967

On the expected gain from adjusting matched term retrieval systems

A file adjustment procedure based on maximizing the Bayes expected gain is proposed for matched term retrieval systems. The expected gain and its probability distribution are derived as a function of: (1) the prior proportion of omitted terms, and (2) the coefficient of separation between two distributions corresponding to values of an adjustment statistic. An example evaluates the gain parameters for a typical information retrieval system.
Research and Advances Aug 1 1967

Contextual understanding by computers

A further development of a computer program (ELIZA) capable of conversing in natural language is discussed. The importance of context to both human and machine understanding is stressed. It is argued that the adequacy of the level of understanding achieved in a particular conversation depends on the purpose of that conversation, and that absolute understanding on the part of either humans or machines is impossible. 0
Research and Advances Sep 1 1965

UPLIFTS—University of Pittsburgh linear file tandem system

A series of computer programs has been developed and is now operational for processing the National Aeronautics and Space Administration linear file system on an IBM 1401-7090 combined data processing system. The programs are noteworthy in that they create fixed length logical records and fixed length blocks from variable length source data, and format the output for optimization of processing on the IBM 7090 system. The programs are completely self-checking and test for both validity and accuracy of the input materials as provided by the National Aeronautics and Space Administration.
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Research and Advances Jul 1 1965

Conventions for the use of symbols in the preparation of flowcharts for information processing systems

This paper is intended as an outline of the various conventions which are being considered for the use of flowchart symbols in the preparation of all types of flowcharts for information processing systems. The conventions are applied to the use of the symbols appearing in the proposed American Standard Flowchart Symbols for Information Processing Systems. This paper is concerned with the use of the proposed American Standard Flowchart Symbols and not with the symbols per se.

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