Donald D. Chamberlin

System R: relational approach to database management

System R is a database management system which provides a high level relational data interface. The systems provides a high level of data independence by isolating the end user as much as possible from underlying storage structures. The system permits definition of a variety of relational views on common underlying data. Data control features are provided, including authorization, integrity assertions, triggered transactions, a logging and recovery subsystem, and facilities for maintaining data consistency in a shared-update environment. This paper contains a description of the overall architecture and design of the system. At the present time the system is being implemented and the design evaluated. We emphasize that System R is a vehicle for research in database architecture, and is not planned as a product.

SEQUEL: A structured English query language

In this paper we present the data manipulation facility for a structured English query language (SEQUEL) which can be used for accessing data in an integrated relational data base. Without resorting to the concepts of bound variables and quantifiers SEQUEL identifies a set of simple operations on tabular structures, which can be shown to be of equivalent power to the first order predicate calculus. A SEQUEL user is presented with a consistent set of keyword English templates which reflect how people use tables to obtain information. Moreover, the SEQUEL user is able to compose these basic templates in a structured manner in order to form more complex queries. SEQUEL is intended as a data base sublanguage for both the professional programmer and the more infrequent data base user.

SEQUEL 2: a unified approach to data definition, manipulation, and control

SEQUEL 2 is a relational data language that provides a consistent, English keyword-oriented set of facilities for query, data definition, data manipulation, and datac ontrol. SEQUEL 2 may be used either as a stand-alone interface for nonspecialists in data processing or as a data sublanguage embedded in a host programming language for use by application programmers and data base administrators. This paper describes SEQUEL 2 and the means by which it is coupled to a host language.

Quilt: An XML Query Language for Heterogeneous Data Sources

The World Wide Web promises to transform human society by making virtually all types of information instantly available everywhere. Two prerequisites for this promise to be realized are a universal markup language and a universal query language. The power and flexibility of XML make it the leading candidate for a universal markup language. XML provides a way to label information from diverse data sources including structured and semi-structured documents, relational databases, and object repositories. Several XML-based query languages have been proposed, each oriented toward a specific category of information. Quilt is a new proposal that attempts to unify concepts from several of these query languages, resulting in a new language that exploits the full versatility of XML. The name Quilt suggests both the way in which features from several languages were assembled to make a new query language, and the way in which Quilt queries can combine information from diverse data sources into a query result with a new structure of its own.

XQuery: a query language for XML

XQuery is the XML query language currently under development in the World Wide Web Consortium (W3C). XQuery specifications have been published in a series of W3C working drafts, and several reference implementations of the language are already available on the Web. If successful, XQuery has the potential to be one of the most important new computer languages to be introduced in several years. This tutorial will provide an overview of the syntax and semantics of XQuery, as well as insight into the principles that guided the design of the language.

A history and evaluation of System R

System R, an experimental database system, was constructed to demonstrate that the usability advantages of the relational data model can be realized in a system with the complete function and high performance required for everyday production use. This paper describes the three principal phases of the System R project and discusses some of the lessons learned from System R about the design of relational systems and database systems in general.

XQuery: An XML query language

The World Wide Web Consortium has convened a working group to design a query language for Extensible Markup Language (XML) data sources. This new query language, called XQuery, is still evolving and has been described in a series of drafts published by the working group. XQuery is a functional language comprised of several kinds of expressions that can be nested and composed with full generality. It is based on the type system of XML Schema and is designed to be compatible with other XML-related standards. This paper explains the need for an XML query language, provides a tutorial overview of XQuery, and includes several examples of its use.

Views, authorization, and locking in a relational data base system

In the interest of brevity we assume that the reader is familiar with the notion of a relational data base. In particular, we assume a familiarity with the work of Codd or Boyce and Chamberlin. The examples in this paper will be drawn from a data base which describes a department store and consists of three relations: EMP(NAME, SAL, MGR, DEPT) SALES(DEPT, ITEM, VOL) LOC(DEPT, FLOOR)

Relational Data-Base Management Systems

Before describing the relational model of data, we will briefly discuss some trends in data-base management which give motivation to the development of the relational model. The first large-scale, machine-readable collections of data were stored on external media such as cards or tape. Beginning in the late fifties and early sixties, data banks were being stored on-line using direct-access devices such as disks. Generalized software packages such as BDAM and ISAM [T2] were developed to aid programmers in accessing the data. During the late sixties and early seventies, the idea of an integrated data-base management system was developed. This concept allowed several applications to share a common bank of data, maintained and protected by a central system. In an integrated data-base environment, the data-base management system (DBMS) provides each application program with its own view of the common data, implements various operators for retrieval and update of data, and resolves interference between concurrent users. The overall trend which is visible in data-base management today is the following: users are becoming increasingly oriented toward the information content of their data, and decreasingly concerned with its repwaenta.tion details. Increasingly, the user interface of a modern DBMS deals with abstract information rather than with the various bits, pointers, arrays, lists, etc., which may be used to represent information. Responsibility for choosing an appropriate representation for the information is being assumed by the system and is not exposed to the end user; indeed, the representation of a given fact may change over time without the user being aware of the change. The general term for this trend away from representation details is data independence. If we attempt to extrapolate the trend toward data independence, we observe that most current DBMS present the user with a view of records connected in some sort of structure, such as a network or hierarchy. In such a view, information may be represented in at least three ways: 1) by the contenls of records (e.g., Smith’s employee record has DEPTNO = 50.); 2) by the connections between records e.g., Smith’s employee record occurs in the hierarchy below the department record for Dept. 50.); and

Human factors evaluation of two data base query languages: square and sequel

Boyce et al. have recently described two data base query languages, SQUARE and SEQUEL, which are intended for use in an interactive mode by both programmers and professional non-programmers (e.g., accountants, lawyers, managers). The languages are comparable in the sense that the basic operators, underlying data structures and intended use are the same. They differ primarily in syntactic form, with a few additional differences in some of the specific features. Both of the languages are intended to be easily learned and used by people without specialized computer training.