The string-to-string correction problem is to determine the distance between two strings as measured by the minimum cost sequence of “edit operations” needed to change the one string into the other. The edit operations investigated allow changing one symbol of a string into another single symbol, deleting one symbol from a string, or inserting a single symbol into a string. An algorithm is presented which solves this problem in time proportional to the product of the lengths of the two strings. Possible applications are to the problems of automatic spelling correction and determining the longest subsequence of characters common to two strings.

http://www.inrg.csie.ntu.edu.tw/algorithm2014/homework/Wagner-74.pdf

The String-to-String Correction Problem

This tutorial paper explores the mechanics of protecting computer-stored information from unauthorized use or modification. It concentrates on those architectural structures-whether hardware or software-that are necessary to support information protection. The paper develops in three main sections. Section I describes desired functions, design principles, and examples of elementary protection and authentication mechanisms. Any reader familiar with computers should find the first section to be reasonably accessible. Section II requires some familiarity with descriptor-based computer architecture. It examines in depth the principles of modern protection architectures and the relation between capability systems and access control list systems, and ends with a brief analysts of protected subsystems and protected objects. The reader who is dismayed by either the prerequisites or the level of detail in the second section may wish to skip to Section III, which reviews the state of the art and current research projects and provides suggestions for further reading.

/pdf/the-protection-of-information-in-computer-systems-2qepizoiqp.pdf

The protection of information in computer systems

Research aimed at correcting words in text has focused on three progressively more difficult problems:(1) nonword error detection; (2) isolated-word error correction; and (3) context-dependent work correction. In response to the first problem, efficient pattern-matching and n-gram analysis techniques have been developed for detecting strings that do not appear in a given word list. In response to the second problem, a variety of general and application-specific spelling correction techniques have been developed. Some of them were based on detailed studies of spelling error patterns. In response to the third problem, a few experiments using natural-language-processing tools or statistical-language models have been carried out. This article surveys documented findings on spelling error patterns, provides descriptions of various nonword detection and isolated-word error correction techniques, reviews the state of the art of context-dependent word correction techniques, and discusses research issues related to all three areas of automatic error correction in text.

Techniques for automatically correcting words in text

: Set theory, Mathematical models, Computer information security, Computer privacy, Computer security, Systems theoryThe paper reports the first results of an investigation into solutions to problems of security in computer systems; it establishes the basis for rigorous investigation by providing a general descriptive model of a computer system. Borrowing basic concepts and constructs from general systems theory, the authors formed a basic result concerning security in computer systems, using precise notions of 'security' and 'compromise'. The authors also demonstrate how a change in requirements can be reflected in the resulting mathematical model. A lengthy introductory section is included in order to bridge the gap between general systems theory and practical problem solving.

https://apps.dtic.mil/sti/pdfs/AD0770768.pdf

Secure Computer Systems: Mathematical Foundations

Approximate matching of strings is reviewed with the aim of surveying techniques suitable for finding an item in a database when there may be a spelling mistake or other error in the keyword. The methods found are classified as either equivalence or similarity problems. Equivalence problems are seen to be readily solved using canonical forms. For sinuiarity problems difference measures are surveyed, with a full description of the wellestablmhed dynamic programming method relating this to the approach using probabilities and likelihoods. Searches for approximate matches in large sets using a difference function are seen to be an open problem still, though several promising ideas have been suggested. Approximate matching (error correction) during parsing is briefly reviewed.

http://www.quretec.com/u/vilo/edu/2002-03/Tekstialgoritmid_I/Articles/Approximate/Hall_Dowling_Approximate_Matching_Review_1980_p381-hall.pdf

Approximate String Matching

Several specialized techniques are shown for efficiently incorporating spelling correction algorithms into compilers and operating systems. These include the use of syntax and semantics information, the organization of restricted keyword and symbol tables, and the consideration of a limited class of spelling errors. Sample 360 coding for performing spelling correction is presented. By using systems which perform spelling correction, the number of debugging runs per program has been decreased, saving both programmer and machine time.

Spelling correction in systems programs

The security of an information system may be represented by a model matrix whose elements are decision rules and whose row and column indices are users and data items respectively. A set of four functions is used to access this matrix at translation and execution time. Distinguishing between data dependent and data independent decision rules enables one to perform much of the checking of security only once at translation time rather than repeatedly at execution time. The model is used to explain security features of several existing systems, and serves as a framework for a proposal for general security system implementation within today's languages and operating systems.

/pdf/on-the-implementation-of-security-measures-in-information-f0f8vo2iq3.pdf

On the implementation of security measures in information systems

Research and Practice in Office Automation.

A general purpose, remote access, computing system is described, that employs twelve-key keyboard telephones as terminals. Audio output is provided directly to the telephone terminah, but the system will normally be used in conjunction with remotely located high speed printing devices. The system is a compatible extension of an existing batch processing system. A significant element of Ihe system is a scheme for transmitting alphanumeric information by single strokes on a numeric keyboard. The programmed scanner uses context to eliminate the ambiguity in transmission.

Tele-CUPL: a telephone time sharing system

A programming structure, language constructs, and supervisorry system organization are proposed for the design and coding of large shared data base systems. The bases for this organization are a generalized interrupt structure and the newly introduced concept of ``file tagging'''', which is the process of associating program structures and interrupt generating conditions with items in the data base. An algorithm for resolving conflicts which arise in scheduling the interrupt processing routines is presented. DPL, a programming language and supervisory system in which these concepts are implemented, is used to illustrate the new organization which is proposed for management information systems. Keywords and phrases: management information systems, integrated data processing, supervisors, interrupts, monitoring systems, supervisory systems, interrupt scheduling, parallel processing.

Howard L. Morgan

Papers

Spelling correction in systems programs

On the implementation of security measures in information systems

Research and Practice in Office Automation.

Tele-CUPL: a telephone time sharing system

An Interrupt Based Organization for Management Information Systems