scispace - formally typeset
Search or ask a question

Showing papers on "String (computer science) published in 1976"


Journal ArticleDOI
TL;DR: It is shown that unless a bound on the total number of distinct symbols is assumed, every solution to the problem can consume an amount of time that is proportional to the product of the lengths of the two strings.
Abstract: The problem of finding a longest common subsequence of two strings is discussed. This problem arises in data processing applications such as comparing two files and in genetic applications such as studying molecular evolution. The difficulty of computing a longest common subsequence of two strings is examined using the decision tree model of computation, in which vertices represent “equal - unequal” comparisons. It is shown that unless a bound on the total number of distinct symbols is assumed, every solution to the problem can consume an amount of time that is proportional to the product of the lengths of the two strings. A general lower bound as a function of the ratio of alphabet size to string length is derived. The case where comparisons between symbols of the same string are forbidden is also considered and it is shown that this problem is of linear complexity for a two-symbol alphabet and quadratic for an alphabet of three or more symbols.

273 citations


01 Mar 1976
TL;DR: This chapter considers the closure properties of the Petri Net Languages, their characterization, their relation to other language families, and the decidability of various problems concerning these languages.
Abstract: In a labeled Petri Net we assign symbols from an alphabet to some or all the transitions of a Petri Net. To each firing sequence of such a Labeled Petri Net corresponds to a string over the alphabet. We study the languages obtained in this way by all firing sequences of a Petri Net, or by all firing sequences which reach a given final marking. We consider the closure properties of these languages, their characterization, their relation to other language families, and the decidability of various problems concerning these languages. The last chapter relates Petri Nets to Counter Automata and Weak Counter Automata, introduces inhibitor Nets and Priority Nets, and considers extensions and limitations of the Petri Net Languages.

246 citations


Journal ArticleDOI
Frank Rubin1
TL;DR: A system for the compression of data files, viewed as strings of characters, is presented, which applies equally well to English, to PL/I, or to digital data.
Abstract: A system for the compression of data files, viewed as strings of characters, is presented. The method is general, and applies equally well to English, to PL/I, or to digital data. The system consists of an encoder, an analysis program, and a decoder. Two algorithms for encoding a string differ slightly from earlier proposals. The analysis program attempts to find an optimal set of codes for representing substrings of the file. Four new algorithms for this operation are described and compared. Various parameters in the algorithms are optimized to obtain a high degree of compression for sample texts.

87 citations


Dissertation
01 Jan 1976
TL;DR: This paper presents a meta-modelling system that automates the very labor-intensive and therefore time-heavy and therefore expensive and expensive process of computer programming called “hacking”.
Abstract: Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

75 citations


Patent
02 Nov 1976
TL;DR: In this paper, an apparatus is used to detect the pitch in a string instrument, comparing it with a known standard, and providing an output error signal to an audio amplifier which drives a motor and gear train.
Abstract: This disclosure pertains to an apparatus utilized to detect the pitch in a string instrument, comparing it with a known standard, and providing an output error signal to an audio amplifier which drives a motor and gear train. The output shaft of the gear train is removably attached to the string tensioning pin. A timer activates the correcting motor in short bursts facilitating the manual striking of the string so as to produce a tone that may be measured. When the motor successfully adjusts the pitch produced by the string, the error signal is reduced sufficiently to prevent further motorized adjustments of the string tension. A meter is provided to indicate the relative pitch produced by the string by displaying the amplitude of the error signal. Locking means prevents the output shaft from being rotated by the motor, thereby enabling the user to manually adjust the pin when desired.

43 citations


Journal ArticleDOI
TL;DR: A context sensitive language over {0, 1} + is described whose words represent straight lines in the plane whose generation and recognition algorithms are of interest for pattern recognition, computer graphics, parallel computation, and neural net theory.

37 citations


Journal ArticleDOI
Trivedi1
TL;DR: DPMIN is defined and proved to be an optimal demand prepaging algorithm and several practical prepaging algorithms are defined which require only a partial knowledge of the future reference string and are shown to reduce the paging problems of array algorithms operating on large arrays.
Abstract: A demand prepaging algorithm DPMIN is defined and proved to be an optimal demand prepaging algorithm. However, it cannot be used in practice since it requires that the future refreence string be completely known in advance. Several practical prepaging algorithms are also defined which require only a partial knowledge of the future reference string. Finally, we show that these prepaging algorithms reduce the paging problems of array algorithms operating on large arrays.

36 citations


Proceedings ArticleDOI
28 Jun 1976
TL;DR: An automatic string placement program used to reorder cells in polycell rows such that channel routing in the adjacent channels is not blocked by cyclic constraints, and the program needs fewer routing tracks.
Abstract: This paper describes an automatic string placement program used to reorder cells in polycell rows such that channel routing in the adjacent channels (a) is not blocked by cyclic constraints, and (b) needs fewer routing tracks. The program utilizes cell reflections and pairwise neighbor exchanges, simultaneously monitoring both the channels immediately above and below the row being reordered. Reductions of 25% in the number of required routing tracks are commonly obtained.

34 citations


Journal ArticleDOI
TL;DR: It is shown that processing is interfered with less when both strings are of the same degree of regularity than when they are not.
Abstract: A model is described for the processing of word-like (regular) and non-word-like (irregular) letter strings in a situation where either type of string may occur. It is proposed that each type of string is processed by specialised routines which are deployed contingently on an initial decision about the regularity of an item. Three experiments involving word/nonword and same/different responses investigate how the processing of a string is affected by the brief exposure of a prior string. It is shown that processing is interfered with less when both strings are of the same degree of regularity than when they are not. The model is revised and extended in the light of the results obtained as well as some theoretical considerations.

32 citations


Journal ArticleDOI
TL;DR: This paper describes a program that learns production systems that take arbitrary strings of LISP atoms as input and produce characterizations of them as output.

30 citations


Book ChapterDOI
01 Jan 1976
TL;DR: This chapter provides an overview, illustrated by a great number of examples, of the syntactic (linguistic) pattern recognition of one-dimensional and high-dimensional grammars.
Abstract: This chapter provides an overview, illustrated by a great number of examples, of the syntactic (linguistic) pattern recognition Languages are used to describe patterns, and syntax analysis procedures are employed as recognition procedures Methods for the selection of pattern primitives are presented Both one-dimensional (string) and high-dimensional grammars are discussed and their applications to one-dimensional and high-dimensional patterns demonstrated Problems for further research are suggested

Patent
23 Jul 1976
TL;DR: In this paper, a single trip method of testing and treating a down hole formation in which conventional drill stem testing can be carried out followed by acidizing or other treatment of the formation without the need to remove the drill stem test string is presented.
Abstract: A single trip method of testing and treating a down hole formation in which conventional drill stem testing can be carried out followed by acidizing or other treatment of the formation without the need to remove the drill stem test string, the method employing a well tool in the operating tool string which allows reverse circulation to clean out the tool string following the initial drill stem test, allows the introduction of acidizing fluid into the formation and permits a second reverse circulation following acidizing and subsequent testing, the well tool being operative without the necessity for rotation of the tool string.

Patent
20 Sep 1976
TL;DR: In this article, a method and apparatus for measuring the energy input to the rod string of a well-pumping unit in real-time was proposed, where the load on the rod-string is multiplied by the velocity of the rodstring and the result integrated over at least a portion of the pump stroke.
Abstract: A method and apparatus for measuring the energy input to the rod string of a well pumping unit in real time wherein the load on the rod string is multiplied by the velocity of the rod string and the result integrated over at least a portion of the pump stroke. The change in the energy input to the well is used to determine when the well has pumped-off.

PatentDOI
TL;DR: In this paper, an electronic sound generating system is disclosed for use with a stringed musical instrument such as a guitar, where a pickup coil is positioned adjacent to the string so that RF signals of varying amplitude are induced in the coil due to vibration of the string resulting from playing of the instrument.
Abstract: An electronic sound generating system is disclosed for use with a stringed musical instrument such as a guitar. An RF oscillator is connected with an electrically conductive string of the instrument and a pickup coil is positioned adjacent to the string so that RF signals of varying amplitude are induced in the coil due to vibration of the string resulting from playing of the instrument. The variable amplitude RF signals are detected and an audio signal produced therefrom that is coupled to a speaker, for example. A stereo output can be provided by placing dual pickup coils adjacent to the string with the pickup coils being positioned normal to one another. Each string of the musical instrument can be separately provided with an RF current of a common frequency or different frequencies. A separate pickup coil is provided for each string, with two such coils being provided for each string if the output is to be a stereo output, and the signals from the pickup coils are processed in separate channels each of which includes a filter tuned to the frequency of the RF signal impressed on the associated string. Thus, separate audio outputs from each string are available for independent signal processing. Conventional techniques may therefore be employed to produce effects normally associated with electronic music synthesizers. In addition, a vibration sustaining device can also be utilized for each string to continue or alter vibration of the string.

Proceedings ArticleDOI
20 Oct 1976
TL;DR: The string scanning facilities of SL5 are described and how they may be used in the analysis and synthesis of strings are illustrated.
Abstract: Advances in the understanding of string pattern matching have led to a coroutine model for scanning procedures that has been the basis for recent work. Motivated by the success of this work, the SL5 programming language has been developed to provide a vehicle for research in these areas. This paper describes the string scanning facilities of SL5 and illustrates how they may be used in the analysis and synthesis of strings.

Journal ArticleDOI
TL;DR: A systematic classification of the effect of nonterminals, letter-to-letter homomorphicisms, nonerasing homomorphisms and homomorphism for all the basic types of deterministic Lindenmayer systems using context is contained.

Patent
10 Dec 1976
TL;DR: An adjustable grip for a compound bow which allows adjustment of draw length without change of a bow structure or string length is presented in this paper, this being accomplished by providing a fore and aft adjustment of the bow grip relative to the main handle portion.
Abstract: An adjustable grip for a compound bow which allows adjustment of draw length without change of a bow structure or string length, this being accomplished by providing a fore and aft adjustment of the bow grip relative to the main handle portion. The grip includes two members extending from a bow handle with a spacer mounted therebetween with slots to permit the spacer to be moved and locked in the direction of the strung bow string and also in the direction toward either of the two members. A grip handle is mounted below the spacer.

Patent
25 Jun 1976
TL;DR: In this paper, a method for making a wound musical instrument string having improved tone quality and life involves the winding of a cover wire onto a core wire followed by a thermal conditioning step in which the string is heated to an elevated temperature for a significant period of time.
Abstract: A method for making a wound musical instrument string having improved tone quality and life involves the winding of a cover wire onto a core wire followed by a thermal conditioning step in which the string is heated to an elevated temperature for a significant period of time.

Proceedings ArticleDOI
20 Oct 1976
TL;DR: A new type of grammar for generating two-dimensional patterns is introduced and several unrelated properties of the classes of patterns generated by various varieties of matrix grammars are announced.
Abstract: A new type of grammar for generating two-dimensional patterns is introduced. The generation of a pattern occurs in two phases. First, a string grammar generates a “row” of syntactic variables (the sequential phase). Then a battery of instances of string grammars—one for each symbol produced in the first phase—operate in tandem to create the columns of the final pattern (the parallel phase). Several unrelated properties of the classes of patterns generated by various varieties of matrix grammars are announced.

Proceedings ArticleDOI
Harvey F. Silverman1, N. Dixon
01 Apr 1976
TL;DR: The problems concerning the diadic segment classification and final string estimation are discussed, and the current solutions given.
Abstract: The Modular Acoustic Processor (MAP), a complex experimental system for automatic derivation of phonemic string output for continuous speech, was first described in April 1974. Many of the new concepts currently in MAP are described. In particular, the problems concerning the diadic segment classification and final string estimation are discussed, and the current solutions given. Results on a large body of continuous speech data, prepared by an automatic evaluation system will also be presented.

Book
01 Jan 1976


01 Jan 1976
TL;DR: The versatility and capabilities of KANDIDATS allow processing of images that are a few thousands rows by a few thousand columns in a minicomputer system with only 32 K words of main memory.
Abstract: KANDIDATS is a comprehensive digital image processing system that interacts with the user at a command string level. It includes prompting for parameter. input .and checks user input for errors. Image analyses available In KANDIDATS consist of utility functions, image transform operations, spatial clustering, and Bayesian classi~ication. The versatility and capabilities of KANDIDATS anse from a modular programming structure and file stru'cture. These attributes allow processing of images that are a few thousand rows by a few thousand columns in a minicomputer system with only 32 K words of main memory. 1.0 IMAGE PROCESSING

Patent
19 Nov 1976
TL;DR: In this paper, a yo-yo toy including two circular blocks joined by a pin having a string wound around it is described, where the pivots joining the additional member to the blocks are on an axis which may be coaxial with the pin axis, or parallel to and spaced from the pin's axis.
Abstract: A yo-yo toy including two circular blocks joined by a pin having a string wound around it. An additional member has portions rotatably mounted on the outer faces of the blocks, so that the additional member moves up and down with the blocks as the yo-yo is used, but does not rotate with the blocks. The additional member may be a human or animal figure, or a representation of a real thing, such as an airplane. The pivots joining the additional member to the blocks are on an axis which may be coaxial with the pin axis, or parallel to and spaced from the pin axis. The additional member may remain above the axis of the pin, may depend below the pin axis, or may extend above and below the pin axis when the blocks are suspended from the string. In the first case, the additional member has a hole through which the string extends.


Book ChapterDOI
01 Jan 1976
TL;DR: A “grammar” is a formal device for specifying a potentially infinite “language” (set of strings) in a finite way by imposing a structure, called a “derivation tree”, on the string generated.
Abstract: A “grammar” is a formal device for specifying a potentially infinite “language” (set of strings) in a finite way. Strings in the lanaguage are generated by starting with a string consisting of one particular “start symbol” and successively rewriting the string according to a finite set of rewriting rules or “productions”. Grammars of interest here impose a structure, called a “derivation tree”, on the string generated. Formally, grammars are defined as follows.

Journal ArticleDOI
TL;DR: The following pages chart a passage through measures 12-17.5 of the Trio, Op. 45, of Schoenberg as discussed by the authors and indicate some of the many paths of progression to, and a few of those away from, these measures, by sightings and soundings, fore and aft.
Abstract: The following pages chart a passage through measures 12-17.5 of the Trio, Op. 45, of Schoenberg. These measures were chosen for examination because they form an intuitively grasped, completed phrase, and because much of what is in them is a synthesis of previous parts of the piece, to be developed in later sections. In the course of viewing mm. 12-17.5 I have tried to indicate some of the many paths of progression to, and a few of those away from, these measures, by sightings and soundings, fore and aft.

Patent
22 Nov 1976
TL;DR: In this paper, the string pulse signals corresponding to optical patterns on the railroad tracks were protected from the landscape off the tracks, external noise, etc., in order to protect the string pulses.
Abstract: PURPOSE:Protection of the string pulse signals corresponding to optical patterns on the railroad tracks from the landscape off the tracks, external noise, etc.


Journal ArticleDOI
TL;DR: An algorithm is discussed which translates two-dimensional mathematical expressions such as subscripting and displayed division into a string form suitable for input to a classical compiler.
Abstract: An algorithm is discussed which translates two-dimensional mathematical expressions such as subscripting and displayed division, that have been prepared using a keyboard input device, into a string form suitable for input to a classical compiler. The algorithm allows reasonably general forms, yet is sufficiently simple to be practically applicable today. It may be used as a preprocessor to an existing compiler in order to improve the readability of an existing language.