ACM Transactions on Database Systems 

About: ACM Transactions on Database Systems is an academic journal published by Association for Computing Machinery. The journal publishes majorly in the area(s): Relational database & Query optimization. It has an ISSN identifier of 0362-5915. Over the lifetime, 958 publications have been published receiving 105025 citations. The journal is also known as: TODS & ACM TODS.

On optimistic methods for concurrency control

Abstract: Most current approaches to concurrency control in database systems rely on locking of data objects as a control mechanism. In this paper, two families of nonlocking concurrency controls are presented. The methods used are “optimistic” in the sense that they rely mainly on transaction backup as a control mechanism, “hoping” that conflicts between transactions will not occur. Applications for which these methods should be more efficient than locking are discussed.

Extending the database relational model to capture more meaning

Abstract: During the last three or four years several investigators have been exploring “semantic models” for formatted databases. The intent is to capture (in a more or less formal way) more of the meaning of the data so that database design can become more systematic and the database system itself can behave more intelligently. Two major thrusts are clear. (1) the search for meaningful units that are as small as possible—atomic semantics; (2) the search for meaningful units that are larger than the usual n-ary relation—molecular semantics. In this paper we propose extensions to the relational model to support certain atomic and molecular semantics. These extensions represent a synthesis of many ideas from the published work in semantic modeling plus the introduction of new rules for insertion, update, and deletion, as well as new algebraic operators.

Database abstractions: aggregation and generalization

Abstract: Two kinds of abstraction that are fundamentally important in database design and usage are defined Aggregation is an abstraction which turns a relationship between objects into an aggregate object Generalization is an abstraction which turns a class of objects into a generic object It is suggested that all objects (individual, aggregate, generic) should be given uniform treatment in models of the real world A new data type, called generic, is developed as a primitive for defining such models Models defined with this primitive are structured as a set of aggregation hierarchies intersecting with a set of generalization hierarchies Abstract objects occur at the points of intersection This high level structure provides a discipline for the organization of relational databases In particular this discipline allows: (i) an important class of views to be integrated and maintained; (ii) stability of data and programs under certain evolutionary changes; (iii) easier understanding of complex models and more natural query formulation; (iv) a more systematic approach to database design; (v) more optimization to be performed at lower implementation levels The generic type is formalized by a set of invariant properties These properties should be satisfied by all relations in a database if abstractions are to be preserved A triggering mechanism for automatically maintaining these invariants during update operations is proposed A simple mapping of aggregation/generalization hierarchies onto owner-coupled set structures is given

The Grid File: An Adaptable, Symmetric Multikey File Structure

Abstract: Traditional file structures that provide multikey access to records, for example, inverted files, are extensions of file structures originally designed for single-key access. They manifest various deficiencies in particular for multikey access to highly dynamic files. We study the dynamic aspects of file structures that treat all keys symmetrically, that is, file structures which avoid the distinction between primary and secondary keys. We start from a bitmap approach and treat the problem of file design as one of data compression of a large sparse matrix. This leads to the notions of a grid partition of the search space and of a grid directory, which are the keys to a dynamic file structure called the grid file. This file system adapts gracefully to its contents under insertions and deletions, and thus achieves an upper bound of two disk accesses for single record retrieval; it also handles range queries and partially specified queries efficiently. We discuss in detail the design decisions that led to the grid file, present simulation results of its behavior, and compare it to other multikey access file structures.

System R: relational approach to database management

Abstract: 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.