Showing papers on "String (computer science) published in 1974"

The String-to-String Correction Problem

Abstract: 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.

String-matching and other products

Abstract: : The string-matching problem considered is to find all occurrences of a given pattern as a substring of another longer string. When the pattern is simply a given string of symbols, there is an algorithm due to Morris, Knuth and Pratt which has a running time proportional to the total length of the pattern and long string together. This time may be achieved even on a Turing machine. The more difficult case where either string may have don't care symbols which are deemed to match with all symbols is also considered. By exploiting the formal similarity of string-matching with integer multiplication, a new algorithm has been obtained with a running time which is only slightly worse than linear. (Author)

String stability of relative-motion PID vehicle control systems

Abstract: An important performance criterion for moving vehicle longitudinal control systems is string stability in the face of perturbations in the motion of individual vehicles. Systems employing a moving-cell reference for each vehicle always exhibit string stability since there is no vehicle interaction within the string. This correspondence investigates the string stability for a class of relative-motion systems where a moving-cell position reference is not available. It is shown that string stability can be achieved only by using both forward and rearward intervehicle separation measurements.

Order-n correction for regular languages

Abstract: A method is presented for calculating a string B, belonging to a given regular language L, which is “nearest” (in number of edit operations) to a given input string a. B is viewed as a reasonable “correction” for the possibly erroneous string a, where a was originally intended to be a string of L. The calculation of B by the method presented requires time proportional to |a|, the number of characters in a. The method should find applications in information retrieval, artificial intelligence, and spelling correction systems.

Syntax-directed least-errors analysis for context-free languages: a practical approach

Abstract: A least-errors recognizer is developed informally using the well-known recognizer of Earley, along with elements of Bellman's dynamic programming. The analyzer takes a general class of context-free grammars as drivers, and any finite string as input. Recognition consists of a least-errors count for a corrected version of the input relative to the driver grammar. The algorithm design emphasizes practical aspects which help in programming it.

Retinal location and string position as important variables in visual information processing

Abstract: Three experiments were conducted to isolate the effects of retinal locus and string position in tachistoscopic letter recognition. Retinal locus proved to be an important variable even when its range was restricted to less than a degree from the center of the fovea. Performance was maximal at the center of the fovea, dropping off rapidly to about 1.5 deg from the center. From that distance on, the decline in performance was quite gradual. String position was also an important factor. Retinal locus and string position interacted in such a way that the end positions were less affected by retinal locus than the middle positions. It was also found that processing order, as distinct from report order, was a significant component of the string position effect.

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

Abstract: 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.

Effect of Vocalization on the Sense of Pitch of Beginning Band Class Students

Abstract: Studies have shown that wind instrumentalists tend to score lower on tests of aural acuity than do string players and pianists. Several explanations have been advanced to explain this deficiency am...

Optimal dencentralized regulation for a string of coupled systems

Abstract: Decentralized regulation for a string of coupled linear systems is studied. Available to each controller is localized information, represented by linear functions of the state. Necessary conditions for the optimal time-invarient linear regulators are established. The theory can be applied for designing simple on-board computers for regulating a string of moving vehicles.

Electronic digital system and method for reproducing languages using the Arabic-Farsi script

Abstract: A system for mechanically reproducing language characters in a cursive form in accordance with the natural style calligraphy of the language. Written letters are characterized by "links" with preceding and following characters, and mathematical rules describe the cursive script in terms of the form each letter takes dependent upon the preceding and following characters. The system includes input means for inserting characters, one at a time, and for providing coded representations of the characters. The coded representations are fed to decoder means which has as an output a selected combination of concatenation properties applicable to the character. Analyzer means analyzes variables dependent on the concatentation properties of a successive string of characters which comprise a character under consideration, a preceding character and a following character. The analyzer means then provides a further coded representation of a particular concatenation property applicable to the character under consideration when the character under consideration is preceded by the preceding character and followed by the following character. The coded representation and the further coded representation are combined in a combining means to provide a composite coded representation containing information relative to a character and to its applicable concatenation properties. Means are provided for converting the composite code to a code suitable for driving output means.

A locally-organized parser for spoken input

Abstract: This paper describes LPARS, a locally-organized parsing system, designed for use in a continuous speech recognizer. LPARS processes a string of phonemes which contains ambiguity and error. The system is locally-organized in the sense that it builds local parse structures from reliable word candidates recognized anywhere in an input utterance. These local structures are used as “islands of reliability” to guide the search for more highly garbledwords which might complete the utterance.

Bowed string instrument trainer

Abstract: A device for training the hand of a bowed string instrument player to correctly hold the bow of the instrument in the form of an element which can be held in the palm of the hand and around which the fingers and thumb are trained by guide channels. The guide channels cause the fingers and thumb to converge in a desired manner to grip the stick of the bow at the frog.

PLAN2D - Towards a Two-Dimensional Programming Language

Abstract: A program in a two-dimensional language is expressed in some diagrammatic, pictorial form, whereas a program in a “normal” language consists of a one-dimensional (linear) string of characters. To put it briefly, in the former case a program is “drawn”, whilst in the latter case it is “written”. A two-dimensional notation has been used or seems to be worthwhile at least in the following areas: 1. Mathematical expressions are much more readable, if their sub- and superscripts, fractional lines, summation and integration signs with lower and upper bounds, etc. can be written in their usual two-dimensional, not in a somehow linearized form. Due to its non-numeric nature PLAN2D does not deal with such features. 2. The most common use of a two-dimensional notation is the representation of control structures, especially with flow charts.+) But there are still other possibilities for exploiting the two dimensions for describing the flow of control in algorithms. Besides the features used in PLAN2D, e.g. parallelism and synchronisation in non-sequential algorithms might be well expressed diagrammatically. No major effort in this direction is known to the authors. 3. Description and manipulation of linked data structures are the main concern of PLAN2D. There is a motivation for that, as simple as convincing: when dealing with linked data structures most programmers develop their algorithms with the aid of diagrams. In /Kn 68/, p. 256 Knuth recommends:“... it is helpful to draw ”before and after“ diagrams and to compare them to see which links need to be changed.” But if these diagrams are so closely related to the problem, why translating them into the linear notation of some programming language instead of using them as programs directly understandable to the computer? So, the basic feature of PLAN2D consists of “before and after” diagrams which are merged into one diagram describing the desired manipulations of links and other entities. Matching the “before” diagram with the data structure is required, i.e. pattern matching is — besides the two-dimensional notation — the most important feature of PLAN2D.

Process of sighting an archery bow

Abstract: A process is provided for sighting an arrow through the separated strands of a bow string. The process includes the manual adjustment of two circular disks, that have been positioned in the string so as to hold the strands separated from each other, along the axis of the string so as to provide adjustable sighting for different users.

Implementation of Data Manipulating Functions on the STARAN Associative Processor

Abstract: Parallel processing data manipulating functions have been widely discussed in the literature. These functions are used to move data from one processing element to another in a parallel manner. A large subset of these functions (shift, flip, shuffle, spread, replicate, close-up) have been implemented as macros on the STARAN S-1000 Associative Processor. An end off shift was found to require 3W to 8W instruction cycles (W is the field width in bits). Other functions have been implemented requiring log2N (N=string length) end off shift operations. Execution times are minimum when string lengths are a power of two. Data manipulation execution times are typically greater than the time required for an array add instruction but much less than required for an array multiply. Aspects of the STARAN architecture as related to the data manipulating functions are discussed.

String path search procedures for data base systems

Abstract: This paper structures algorithms for the translation of set theoretic queries into procedures for the search of arbitrary complex networks constructed on a data base using three basic types of strings. A method for parametrization of queries which is appropriate for accessing string structures is outlined and it is shown how the properties of string structures can be used to construct an algorithm for finding a search path with minimum path cardinality for a given query addressed to such a network. (The term data management system is used instead of data base management system.)

A parenthesis machine for string manipulation

Abstract: — A parenthesis machine, provided with a stack and an auxiliary memory, is descrihed and then used for : 1) The évaluation of programs of a scheme P of parenthesis languages. 2) The implementation of a gênerai bottom-up analyzer for context-free, total precedence languages. INTRODUCTION This paper describes a parenthesis machine, provided with a stack and an auxiliary memory, which can be used as a string manipulator. This parenthesis machine rewrites a séquence of symbols, belonging to a given alphabet, on the stack. A right parenthesis interrupts this rewriting and acts as a replacement command for the substring enclosed between this parenthesis and the corresponding left one. Such a replacement dépends on the memory state and, in its turn, can modify it. A pioneer work in this field is that of Dijkstra [5], in which the rôle of the right parenthesis is played by the character « E ». The present work is an improvement, essentially because : /) the addition of left parentheses allows the string to be substituted to be of arbitrary length ; iï) the existence of an auxiliary memory gives much greater freedom in writing programs. The present parenthesis machine has been used with some modifications for the réduction of X-formulas to their principal |3-r|-normal forais, should they exist [2] [3]. In the present paper this parenthesis machine is described (section 1) (1) Istituto di Scienza deU'Infbrmazione, Torino. Revue Française d'Automatique, Informatique et Recherche Opérationnelle n° déc. 1974, R-3. 38 M. DEZANI-CIANCAGLINI and then directly applied. Section 2 shows a scheme P of parenthesis languages, solving some programming problems, such as : 1 ) the recursive calls of procedures with uniform conventions ; 2) the transmission of parameter values. Lastly, section 3 exhibits the embedding of a gênerai bottom-up analyzer for context-free, total precedence languages in this parenthesis machine. 1. A PARENTHESIS MACHINE We consider a parenthesis machine consisting of a stack and an auxiliary memory, that is a set of < name, value > pairs (environment). The elementary actions of this machine are the copying of a string onto the stack and the interprétation of a given string as a command. The commands can modify the memory state, which in its turn détermines the process of the computation because every « name » enclosed by a pair of parentheses at the top of the stack is replaced by the corresponding « value ». The machine évaluâtes a string built from an alphabet together with a legitimate use of parentheses which subdivide it arbitrarily. This string is copied from left to right on the stack until the first right parenthesis is reached. The point of interruption of copying is, as usual, denoted by a pointer. The right parenthesis constitutes the order to interpret the substring, enclosed between it and the çorresponding left parenthesis, as a command. For this purpose it is sufficient (with regards to the parenthesis structure) that the string be « dynamically » legal, i.e., that the strings written onto the stack have legal parenthesis structures (), which does not necessarily imply that the input string be « statically » legal, i.e., that it itself, have a legal parenthesis structure. This balance between the number of left and right parentheses has one exception; to make possible the élimination of the go to (see section 2.2) we assume, naturally enough, that a right parenthesis, to which no left parenthesis corresponds, acts as a STOP command. EXAMPLE. The following is an example which, although not çorresponding to any programming language, shows the évaluation technique of this machine. Let us ^assume that every string which does not occur as a « name » in the environment must be replaced on the stack with itself. We now give the successive stack configurations for the évaluation of the string : (1(42)(3(114)5)(6(78)8)) (1) We say that a parenthesis structure is legal iff, scanning it from left to right, the number of left parentheses is always not less than the number of right parentheses, and they are equal at the end of the structure. Revue Française d'Automatique^ Informatique et Recherche Opérationnelle A PARENTHESIS MACHINE FOR STRING MANIPULATION when the environment consists of the following pairs : < 42,1 > < 78,3 > < 114,2 > < 325,1 >< 111638,5 > 39 stack configurations pointer positions (1(42)T(3(114)5)(6(78)8)> (11(3(114) (11(325) (111(638) (111638) 5 (1(42)(3<114)5)T(6(78)8)> (1<42>(3(114)5)<6<78)*8)> (l(42)O(114)5)(6<78)8)t) (l(42)(3(114)5)(6(78)8))t (l(42)(3(lU)5)(6(78)8))t The string evaluated in this example has a statically légal parenthesis structure. Examples of programs with parenthesis structures only dynamically légal are given in section 2. 2. A SCHEME P OF PARENTHESIS LANGUAGES Let us describe a scheme P of parenthesis languages. Every program of this scheme consists of a string of a given alphabet inerged into a parenthesis structure dynamically légal (the only exception being a right parenthesis without a corresponding left one which acts as STOP command). The types of strings, which can occur enclosed in a parenthesis pair at the top of the stack, Le., the types of commands, are six. Each is replaced uniquely at the top of the stack by a given string and can modify the environment. The following table lists the six types of strings, the strings replacing each one of these on the stack top, and the possible modifications of the environment :

Method for retrieving a severed pipe string from a well

Abstract: Method and apparatus for retrieving a severed pipe string remaining in a well including milling apparatus for milling the upper, flattened end of the remaining pipe string in order to prepare the end for grappling by a grappling device and thereafter retrieving the pipe string with the grappling device.

A Locally Organized Parser for Spoken Input

Abstract: A locally organized parsing system (LPARS) has been developed for use in a continuous speech recognizer, accepting as its input a string of phonemes which contains ambiguity and error. The system is locally organized in the sense that it can construct local parse structures from word candidates recognized fairly reliably in all parts of an input utterance. These local structures are used as “islands of reliability” and serve as context to guide the search for more highly garbled words which might complete the utterance.

The Lexical Subclasses of the Linguistic String Parser

Abstract: Thc N T T T Linguistic String 1>arscr (1,SI') is a ~vorldng system for the syntactic analysis of Ehglish scicntifie tests. It consists of a parsing program, a large-coverage b~glish grammar , and a Icsicon. Thc gramnlarls effcctivcncss in parsing texts is due in large part to a substantial Imdy of detail cvl \vc.Il-formedness rcst rictions which eliminate most incorrect syntactic parses which would be allo~vecl by a weaker grammar. The restrictions mainly test for compatible combinations of word subclasses. This paper dcfines the 109 adjective, noun and verb suhclasscs. These subolasses, as \'ell as others not prcscnted herc, are defined Ln such a way that they can he used as a guide for dassifymg new entries to the LSP lexicon and as a lingpistic reference twl. Fach definition lncludcs a statement of the intent of tllc subclass, a diawostic frame, sentence examples and a worcl list draun from tho present dictionary. The subclasses are defined tro reflect precisely the grammatical propertics tested for by the restrictiol~s of the grammar Where necessary for clariking the intent of the subclass, three additiollal criteria are employed: excision, implicit and co-rcfcrcncc, and paraphrase. The subclasscs have been defined so as to be consistent with a subsecluent stage of transformational analysis rilzicl~ is currently being imp1 e-mentd.

On the Modeling of Demand Paging Algorithms by Finite Automata

Abstract: Two finite automata are devised for modeling two classes of demand paging algorithms. The first one of one input and three outputs models the class of algorithms with a constant amount of allocated space. The second one of one input and six outputs models the class of algorithms with a variable amount of allocated space. Some evaluation techniques are developed following each model. The memory states of the first class algorithm with the Least Recently Used (LRU) replacement policy and the working set model of the second class are recursively defined by strings of the loaded pages. The adopted replacement policy and the state string updating procedure are imbedded in the recursive definition of memory states. Properties of some algorithms are developed to fit the finiteness assumption of a reference string.

Deterministic Lindenmayer languages, nonterminals and homomorphisms

Abstract: Lindenmayer systems are a class of parallel rewriting systems originally introduced to model the growth and development of filamentous organisms. Families of languages generated by deterministic Lindenmayer systems (i.e., those in which each string has a unique successor) are investigated. In particular, the use of nonterminals, homomorphisms, and the combination of these are studied for deterministic Lindenmayer systems using one-sided context (D1Ls) and two-sided context (D2Ls). Languages obtained from Lindenmayer systems by the use of nonterminals are called extensions. Typical results are: The closure under letter-to-letter homomorphism of the family of extensions of D1L languages is equal to the family of recursively enumerable languages, although the family of extensions of D1L languages does not even contain all regular languages. Let P denote the restriction that the system does not rewrite a letter as the empty word. The family of extensions of PD2L languages is equal to the family of languages accepted by deterministic linear bounded automata. The closure under nonerasing homomorphism of the family of extensions of PD1L languages does not even contain languages like {a1,a2,⋯, an}∗--{λ}, n⩾2 . The closure of the family of PD1L languages under homomorphisms which map a letter either to itself or to the empty word is equal to the family of recursively enumerable languages. Strict inclusion results follow from necessary conditions for a language to be in one of the considered families. By stating the results in their strongest form, the paper contains a systematic classification of the effect of nonterminals, letter-to-letter homomorphisms, nonerasing homomorphisms and homomorphisms for all the basic types of deterministic Lindenmayer systems using context.

Some semantically closed languages

Abstract: 1. For some time two main obstacles have been seen to stand in the way of the formalization of natural languages. The first is the difficulty in specifying "rules of formation" for natural languages, that is in giving some effective procedure for determining whether or not an arbitrary string of symbols is a well formed or meaningul sentence with regard to a certain language. Recently progress has been made by various people, Chomsky and Montague, for example, in dealing with this problem. The second obstacle stems from the fact that natural languages are universal, or semantically closed, in that they are capable of at least expressing semantical concepts which apply to themselves. It is to this feature that Legniewski traced the rise of the semantical antinomies. In the mono-