Variable Length Fields Research Articles

Horn Binary Serialization Analysis

A bit layout is a sequence of fields of certain bit lengths that specifies how to interpret a serial stream, e.g., the MP3 audio format. A layout with variable length fields needs to include meta-information to help the parser interpret unambiguously the rest of the stream; e.g. a field providing the length of a following variable length field. If no such information is available, then the layout is ambiguous. I present a linear-time algorithm to determine whether a layout is ambiguous or not by modelling the behaviour of a serial parser reading the stream as forward chaining reasoning on a collection of Horn clauses.

Simon Fraser University Computer Produced Map Catalogue

An IBM 360/50 computer and magnetic tape are used in a new univer- sity library to produce a map catalogue by area and up to six subiects for each map. Cataloguing is by non-professional staff using the Library of Congress "G, schedule. Author, title, and publisher are in variable length fields, and codes are seldom used for input or interpretation. Ma- chine searches by area, subjects, author, publisher, scale, pro-;ection, date and language can be carried out.

Construction and application of covariance functions with variable length-fields

This article focuses on construction, directly in physical space, of three-dimensional covariance functions parametrized by a length-field, and on an application of these functions to improve the representation of the Quasi-Biennial Oscillation (QBO) in the Goddard Earth Observing System, Version 4 (GEOS-4) data assimilation system. The covariance functions are obtained by fusing collections of auto-covariance functions having different constant length-scales with their associated cross-covariance functions. This construction yields covariance functions with length-scales that can vary arbitrarily over any finite partition of the spatial domain. A simple, and also motivating application of these functions is to the case where the length-scale varies in the vertical direction only. The class of covariance functions with variable length-fields constructed in this article will be called multi-level to associate them with this application. The multi-level covariance functions extend well-known single-level covariance functions depending only on a constant length-scale. Generalizations of the familiar first-and third-order autoregressive covariances in three dimensions are given, providing multi-level covariances with zero and four continuous derivatives at zero separation, respectively. Multi-level piecewise rational covariances with two continuous derivatives at zero separation are also provided. Multi-level power-law covariances are constructed with continuous derivatives of all orders. Additional multi-level covariance functions are constructed using the Schur product of single- and multi-level covariance functions. A multi-variate, multi-level power-law covariance with a large troposphere-to-stratosphere length-field gradient is employed to reproduce the QBO from sparse radiosonde wind observations in the tropical lower stratosphere. This covariance model is described along with details of the assimilation experiments. The new covariance model is shown to represent the vertical wind shear associated with the QBO much more effectively than the multi-variate, multi-level covariance model in the baseline GEOS-4 system. Copyright © 2006 Royal Meteorological Society

Overflow/underflow-free floating-point number representations with self-delimiting variable-length exponent field

A class of new floating-point representations of real numbers, based on representations of the integers, is described. In the class, every representation uses a self-delimiting representation of the integers as a variable length field of the exponent, and neither overflow nor underflow appears in practice. The adopted representations of the integers are defined systematically, so that representation's of numbers greater than one have both exponent-significant and integer-fraction interpretations. Since representation errors are characterized by the length function of an underlying representation of the integers, superior systems in precision can be easily selected from the proposed class. >

Analysis of overflow handling for variable length records

Although files with variable length records are very frequent in actual databases due to variable length fields, missing attribute values, multiple values of an attribute and compression, little has been reported in the literature about file structures appropriate for variable length records. In this paper we describe and analyze several overflow handling techniques for the case when records are of variable length. We develop analytic models that take into account variable length records and study the performance in the context of indexed sequential (ISAM) files. We also propose a new overflow handling technique and show that it provides an incremental reorganization capability appropriate for handling variable length records. Analytic results demonstrate that its performance is better than the performance of previous methods. The overflow handling techniques and the analytic methods developed in this paper are also applicable to other file structures with variable length records that require overflow handling.

Inmagic

Now in its seventh major version, the Inmagic database, retrieval and application development software provides a continuously improved system for the library, information centre or any organisation requiring a powerful, variable length field and record database system with powerful Boolean search and complex report generation facilities. The Companion package, Biblio, features predefined database definitions and reports applicable to the library automation situation as well as an excellent tutorial and learning package for any user of the Inmagic software.

RE:Views

3by5 is a database management program that offers versatility and simplicity in entering and manipulating free‐text and/or structured data. The program can manipulate data with variable length fields and is therefore particularly appropriate for managing information with a high text content such as bibliographic citations. OCLC Micro readers should already be familiar with Version 1.0, which was originally released as a “freeware” or “share‐ware” program. It was distributed by OCLC with the May 1985 issue of OCLC Micro (OCLC ♯12129479).

68000 and the Pick operating system

The Pick operating system was developed 20 years ago and has always been thought of as a ‘dark secret’. However, it has been ported onto the 68000 chip, and is proving successful on micros. It is based on a database design, and features variable length fields and the ability to have multivalues. Programming can be carried out in Data BASIC.

Implications of structured programming for machine architecture

Based on an empirical study of more than 10,000 lines of program text written in a GOTO-less language, a machine architecture specifically designed for structured programs is proposed. Since assignment, CALL, RETURN, and IF statements together account for 93 percent of all executable statements, special care is given to ensure that these statements can be implemented efficiently. A highly compact instruction encoding scheme is presented, which can reduce program size by a factor of 3. Unlike a Huffman code, which utilizes variable length fields, this method uses only fixed length (1-byte) opcode and address fields. The most frequent instructions consist of a single 1-byte field. As a consequence, instruction decoding time is minimized, and the machine is efficient with respect to both space and time.

MARC II and COBOL

A description of the machine processing of MARC II records using COBOL for an application on the Library of Congress System 360/30. Emphasis is on the manipulation by COBOL of highly complex variable length MARC records containing variable length fields.