Morton M. Astrahan

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 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.

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.

Support for repetitive transactions and ad hoc queries in System R

System R supports a high-level relational user language called SQL which may be used by ad hoc users at terminals or as an embedded data sublanguage in PL/I or COBOL. Host-language programs with embedded SQL statements are processed by the System R precompiler which replaces the SQL statements by calls to a machine-language access module. The precompilation approach removes much of the work of parsing, name binding, and access path selection from the path of a running program, enabling highly efficient support for repetitive transactions. Ad hoc queries are processed by a similar approach of name binding and access path selection which takes place on-line when the query is specified. By providing a flexible spectrum of binding times, System R permits transaction-oriented programs and ad hoc query users to share a database without loss of efficiency. System R is an experimental database management system designed and built by members of the IBM San Jose Research Laboratory as part of a research program on the relational model of data. This paper describes the architecture of System R, and gives some preliminary measurements of system performance in both the ad hoc query and the “canned program” environments.

System R: an architectural overview

We have described the architecture of System R, including the Relational Data System and the Research Storage System. The RDS supports a flexible spectrum of binding times, ranging from precompilation of “canned transactions” to on-line execution of ad hoc queries. The advantages of this approach may be summarized as follows: 1. For repetitive transactions, all the work of parsing, name binding, and access path selection is done once at precompilation time and need not be repeated. 2. Ad hoc queries are compiled on line into small machine-language routines that execute more efficiently than an interpreter. 3. Users are given a single language, SQL, for use in ad hoc queries as well as in writing PL/I and COBOL transaction programs. 4. The SQL parser, access path selection routines, and machine language code generator are used in common between query processing and precompilation of transaction programs. 5. When an index used by a transaction program is dropped, a new access path is automatically selected for the transaction without user intervention.

Data structures and accessing in data-base systems: I evolution of information systems

The attention of the computer user community is increasingly focusing on data bases and computerized information systems because of two converging trends. Computerized information systems are coming to play an essential role in business operations, and the hardware and software technology for supporting information systems is in a period of rapid technical progress. In spite of this attention, there is still little common agreement as to what information systems are, the functions they perform, and — from a technical point of view -how they should be designed, implemented, installed, and used. These conditions arise naturally from the newness of the field and the ad hoc nature of existing Computerized implementations. A compounding factor is the wide variety of perspectives of those who discuss information systems — for example, the executive, the management consultant, the systems analyst, the mathematician, and the systems programmer. In this paper, we emphasize aspects of information systems that are of importance to systems analysts, systems designers, and implementors.

Approximating the number of unique values of an attribute without sorting

Abstract Counts of unique values are frequently needed information in database systems. Especially, they are essential in query optimization and physical database design. Traditionally, exact counts were obtained by sorting, which is an expensive operation. In this paper we present three algorithms for counting unique values by probabilistic methods. These algorithms require only one pass over the data, and produce approximations to the true count with certain standard deviations. For deviations acceptable in practical environments (~10%), the algorithms require only modest amounts of memory space and computation time. We have implemented all three algorithms in System R. We also present the results of the experiments on accuracy and performance of these algorithms.

Concepts of a Data Independent Accessing Model

The Data Independent Accessing Model (DIAM) represents a constructive combination of the formal mathematical and the evolutionary pragmatic approaches to a Generalized Data Base Management System. It aims at a complete separation between the users (application programmers) model of real-world objects, events, and the relationships among them, and the internal representation of those objects, events, and relationships. At the same time, it aims at complete flexibility of internal representation in terms of simple specifications, the effects of which are easy to understand. The DIAM encompasses four levels of descriptive models (Figure 1), each providing for flexible augmentation of the descriptions of the preceding level. Specifications at each level are retained in a catalog.

Specifications in a Data Independent Accessing Model

The Data Independent Accessing Model (DIAM) Project of the Information Sciences Department of IBM Research is directed towards developing an architectural basis for an advanced data base system - a data base system which, in addition to providing advanced functional capabilities and a new level of data independence, is not limited either in the access paths which can be declared (in order to support the user-specified information collections) or in the encodings which are possible for those access paths. We have already been presented with a general overview of the basic system (1). In that overview, DIAM was seen to be composed of 4 basic levels of description: the Entity Set Model the String Structure Model the Encoding Model the Physical Device Model. In this paper we shall concentrate on the middle two of these levels - the String Structure and the Encoding Models.

Logical design of the digital computer for the SAGE system

Special design features and performance criteria are described for the logical system in the digital computer used in the SAGE (Semi-Automatic Ground Environment) air defense system. Design details are given for the arithmetic element, high-speed multiply, index registers, input-output control, and magnetic drum buffer. The system is designed according to special military application requirements of speed, capacity, reliabiity and flexibility.