The authors characterize the notion of heterogeneous databases as the inevitable consequence of replacing the traditional data processing practice with modern database management. They articulate the current problems and future issues connected with the great proliferation and overwhelming use of heterogeneous databases and their DBMS (database management systems). They survey available DBMS solutions to these problems and issues. The limitations and advantages of various DBMS solutions are examined. To this end, a taxonomy of DBMS solutions to the problems and issues of heterogeneous databases is presented. Some of the current research and proposals on the heterogeneous-database solutions are discussed in the context of the taxonomy.>

An approach to the design of a database system, the multilingual database system (MLDS), has been proposed and implemented. MLDS is a single database system that can execute may transactions written respectively in different data languages and support many databases structured correspondingly in various data models, i.e. DL/I transactions on hierarchical databases, CODASYL-DML transactions on network databases, SQL transactions on relational databases, and Daplex transactions on functional databases. The authors describe MLDS, focusing on its motivation and structure. It is shown how MLDS, by providing an integrated environment for experimenting with data models and data languages, also serves as a testbed that provides insight to data models and data-model semantics, using qualitative and quantitative techniques. Related work on data-language comparison and analysis is indicated.>

This paper introduces a new and unconventional approach to the design and implementation of a database system, the multi-lingual database system (MLDS). The multi-lingual database system is a single database system that can execute many transactions written respectively in different data languages and support many databases structured correspondingly in various data models, i.e., DL/I transactions on hierarchical databases, CODASYL-DML transactions on network databases, SQL transactions on relational databases and Duplex transactions on functional databases. Thus, a multi-lingual database system allows the old transactions and existing databases to be migrated to the new environment, the experienced user to continue to utilize certain favorite features of existing data languages and data models, the new user to explore the strong features of the various data languages and data models, the hardware upgrade to be focused on a single system instead of a heterogeneous collection of database systems, and the database application to cover wider types of transactions and different modes of interactions.

The study of the relationship of the database system and the operating system can best be characterized in terms of their issues on resource management and language support. In this paper the similarities and differences of these two types of systems (i.e., database systems and operating systems) on resource management and language support are articulated. It is hoped that this articulation can point out the new and future database-system research and development areas.

Traditional database systems have long been plagued by performance problems when there is either an increase in the mainframe usage or in the database applications. Solutions to these problems have been sought, first, by offloading the database system from the mainframe computer to a single, dedicated backend computer. The backend computer has its own disk storage, is used to perform all of the database operations, and interacts with the mainframe. However. database systems with this software single-backend approach still encounter the performance problems when either the backend usage or database applications increase. The software multiple-backend approach to database management and hardware upgrade is therefore proposed to overcome the performance-gains and capacity-growth problems of either traditional mainframe-based database systems or conventional software single-backend database systems. In this paper we specify the design requirements and issues of the software multi-backend database systems. We show how these requirements and issues affect the design and implementation of a multi-backend database system known as MBDS. Since MBDS is designed specifically for performance gains, capacity growth, and hardware upgrade, we benchmark MBDS in order to verify whether its design and implementation can indeed relate the gains and growth directly to the multiplicity of backends in terms of the response-time reduction and invariance.

manipulation languages; language processing; analysis and classification of data; database utilities; data translation techniques; distributed database problems and techniques; database recovery and restart; database restructuring; adaptive data structures; concurrent access techniques; database computer hardware architecture; performance and evaluation; intelligent front ends; and related subjects such as privacy and economic issues.

Database computers are special-purpose storage and processing devices which are intended to relieve the database management (software) systems running on the general-purpose computers and provide improved storage and processing capabilities (via hardware) for the existing and new database application. However, to support existing database applications, two steps must be followed. First, the existing database must be transformed into the storage format of the new database computer. This one-time tranformation, known as database transformation, is required to preserve the semantics of the database and to take advantage of the advanced hardware features of the new computer. Second, the database sublanguage used in the existing application programs must be supported in real time by the new database computer so that application programs may be executed in the new environment without the need of program conversion. Such real-time translation of sublanguage calls to the instructions of the new database computer, known as query translation, must be straightforward with minimal software support.

Design considerations of a database computer are presented in this paper. The overall architecture of the computer as well as the organization of its individual components are discussed. Several key concepts which are vital to database management are incorporated in the design and organization of the components. The concepts of tracks-in-parallel read-out and logic-per-some-track processing are provided in an on-line database store for the purpose of achieving high-volume content-addressability. The use of auxiliary information about the database for access precision and control has resulted in the design of a structure memory, an array of content-addressable memory and processor pairs, for large collections of indices. The choice of technologies for the implementation of these components is considered in terms of their cost and performance. Modified moving-head disk technology is chosen in order to support the very large on-line database store. Emerging technologies such as magnetic bubbles and CCD's are chosen for the structure memory on the basis of their matching performance with the on-line database store and their capability for parallel-in-blocks-and-serial-within-block processing. Five other important components are also disdissed in the paper. Their role in the database computer and relationship with the structure memory and on-line database store are delineated.

Data items in a database are semantically related. Thus, the access control mechanism of a database system must be concerned with the possibility that access to one item may violate a denied access to another item. This study concentrates on two basic semantic relations for protection requirements. By utilizing a graph-theoretic approach, some of the fundamental properties of the protection relations can be readily identified. These properties can then be used as a basis for understanding more general context dependent protection requirements. Two fundamental properties of the two protection relations are found. The first property addresses the question: given a database with a set of protection relations, is it possible to find a maximal subset of the database such that access to one item of the subset will not lead to any violation of a denied access to another item? The second property addresses the question: given a database with a set of protection relations, is it possible to find a sequence of accesses such that the protection requirement is enforced with no violation?

This tutorial is extracted from the recently completed monograph, Computer Security: Its Problems and Solutions [3], and is intended as a technical review of research in the areas of operating system security. Furthermore, it is intended to provide some assessment and evaluation of the work reviewed. Some projections and speculations of future activities in operating system research are also included. Because the tutorial is written for technical people who are not directly conducting such research, we have tried to present the review in an illustrative manner with intuitive and informal definitions of the necessary technology. The tutorial expounds the notion of surveillance in terms of logging and threat monitoring. It conceptualizes the problems and solutions of access control. To achieve security, the operating system relies on isolation. The tutorial points out the trade-off between security and cost of isolation. Furthermore, it illustrates two impor tant isolation methods. In order to provide security, the operating system must be designed and implemented as a secure system. The use of verification techniques for proving the correctness of secure operating system design and implementation is examined. When the operating system is large and the security requirements are elaborate, it may be necessary to concentrate the secure elements in a kernel. The notion of secure kernel is therefore examined. Other methods such as penetration tests are also examined An up-to-date bibliography since 1974 is included. To allow the readers to have a coherent coverage of various topics of operating system security, we have endeavored to give our personal views of various subject matters. We would like the reader to bear with us in the expression of these views.

The concepts and capabilities of a database computer (DBC) are given in this paper. The proposed design overcomes many of the traditional problems of database system software and is one of the first to describe a complete data-secure computer capable of handling large databases. This paper begins by characterizing the major problems facing today's database system designers. These problems are intrinsically related to the nature of conventional hardware and can only be solved by introducing new architectural concepts. Several such concepts are brought to bear in the later sections of this paper. These architectural principles have a major impact upon the design of the system and so they are discussed in some detail. A key aspect of these principles is that they can be implemented with near-term technology. The rest of the paper is devoted to the functional characteristics and the theory of operation of the DBC. The theory of operation is based on a series of abstract models of the components and data structures employed by the DBC. These models are used to illustrate how the DBC performs access operations, manages data structures and security specifications, and enforces security requirements. Short Algol-like algorithms are used to show how these operations are carried out. This part of the paper concludes with a high-level description of the DBC organization. The actual details of the DBC hardware are quite involved and so their presentation is not the subject of this paper. A sample database is included in the Appendix to illustrate the working of the security and clustering mechanisms of the DBC.

The concept of the data utility as a database system capable of supporting a data model, a large-scale on-line store, and concurrent user access has emerged in recent years. New technology can make the notion of database computers—a specialized hardware system for database use—a viable one. A summary of previous activities and a discussion of the state of the art of database computers is given. An attempt is made to suggest guidelines for future database computer architecture research.

Record-keeping and decision-making in industry and government are increasingly based on data stored in computer processable databases. Thus the need for improved computer technology for building, managing, and using these databases is clearly evident. This need is particularly acute in a complex society where the interrelationships among various aspects of the society must be identified and represented. The data which must be used to represent these relationships are growing more complex in nature and becoming greater in size. Furthermore, the increasing on-line use of computer systems and the proliferation and mass introduction of multilevel secondary storage suggests that future computer systems will be primarily oriented toward database management. The large size of future on-line databases will require the computer system to manage local as well as physical resources. The management of logical resources is concerned with the organization, access, update, storage, and sharing of the data and programs in the database. In addition, the sharing of data means that the database system must be capable of providing privacy protection and of controlling access to the users' data. The term data is interpreted broadly to include textual, numeric, and signal data as well as data found in structured records. The aim of ACM Transactions on Database Systems (TODS) is to serve as a focal point for an integrated dissemination of database research and development on storage and processor hardware, system software, applications, information science, information analysis, and file management. These areas are particularly relevant to the following ACM Special Interest Groups: Business Data Processing (SIGBDP), Information Retrieval (SIGIR), and Management of Data (SIGMOD). TODS will also embrace parts of the Management/Database Systems and the Information Retrieval and Language Processing sections of Communications of the ACM . High quality papers on all aspects of computer database systems will be published in TODS. The scope of TODS emphasizes data structures; storage organization; data collection and dissemination; search and retrieval strategies; update strategies; access control techniques; data integrity; security and protection; design and implementation of database software; database related languages including data description languages, query languages, and procedural and nonprocedural data manipulation languages; language processing; analysis and classification of data; database utilities; data translation techniques; distributed database problems and techniques; database recovery and restart; database restructuring; adaptive data structures; concurrent access techniques; database computer hardware architecture; performance and evaluation; intelligent front ends; and related subjects such as privacy and economic issues.

A generalized record organization is proposed from which many flxed and variable length records of hierarchical and network formats can be derived. In developing the generalization, attempts are made to characterize the record organization. By identifying the characteristics of the record organization, it is possible to segregate, for storage, the global record structural information from the local and nonstructural information. Such a segregation can lead to more efficient use of storage, ease of reorganizing the records, and the possibility of multiple organizations for the same set of records. A scheme for specifying the generalized record organization is provided and illustrated.