Ali Orooji

A Message-Oriented Implementation of a Multi-Backend Database System (MDBS)

In this paper we describe the communication mechanisms for a mufti-backend database system (MDBS). MDBS is designed to provide for capacity growth and performance enhancement by the addition of more backend minicomputers and associated disks and by the replication of the same software without additional programming. MDBS has been implemented using a permanent process for each major database system function. Further, the processes in a backend are identical to the processes in another backend. The communication functions in MDBS involve interprocess and interbackend mechanisms for control and synchronization. Our primary purpose is to analyze the implementation decisions for the communication mechanism and to describe MDBS from the communications viewpoint.

A relational object-oriented management system

The authors describe the different approaches for supporting the various types of data and users that a company may have. They present a system overview of ROOMS (relational object-oriented management system) and discuss the methods that must be added to user-defined classes in order for them to be used in ROOMS. The options available for the record structure and the five basic relational algebra operations are covered. The authors provide a brief introduction to an encapsulated object-oriented programming system (EOOPS). EOOPS helps to solve the implementation problems that have been encountered in developing ROOMS and that should also be helpful in developing any large object-oriented application.<<ETX>>

Experiments with Data Access and Data Placement Strategies for Multi-Computer Database Systems

The software-oriented multi-computer database systems are characterized by a set of processing elements (PEs) which run identical software and operate on a partitioned database in parallel. Performance improvements and capacity growth can be achieved in this type of system by adding more PEs to the configuration and replicating the existing software on the new PEs.

The case for encapsulated inheritance

Object-oriented programming (OOP) is rapidly gaining attention as a potential approach to nearly any computer software project. Two of the key features of OOP are encapsulation and inheritance. There are, however, several problems that occur when inheritance is allowed to violate encapsulation. The authors present these problems, highlighting their impact on the software development and maintenance processes, along with our proposed solutions to them.<<ETX>>

Predictive performance analysis of multi-computer databases system

Abstract The multi-computer design has been proposed as an approach to the management of very large databases. This type of system is intended to provide for performance improvements and capacity growth. However, realization of the design goals in a system of this type depends upon resolution of hardware and software design questions regarding physical system configurations, data access, data placement and directory management. The ability of proposed solutions to satisfy design questions can be gauged, at low risk and relatively little cost, through the performance of system simulation models. In this paper we describe the development of an open-queuing network simulation model for a software-oriented multi-computer database system, and the results of a predictive performance analysis of the system.

ORR: object-relational rapprochement

The current fashion in database technology is the eschewing of relational databases in favor of object-oriented databases. C.J. Date and Hugh Darwen (1995) have issued a challenge for the industry to turn away from todays relational database products and to begin to develop and use databases conforming to the formal relational model. To meet the storage requirements of modern data, they propose to extend the notion of domains, and they claim that this expanded notion, when combined with the formal relational model, would be more than sufficient for the vast majority of the applications now being moved to object-oriented databases. This paper makes a brief survey of the relational model, object orientation in programming, and some of the present attempts to combine the two. It then presents ORR, a prototype implementation of a database system that incorporates a version of the expanded notion of domains into a near relational database.

A symmetrical approach to granting and revoking access rights in database management systems

The concept of independent revocation is described where an authorizer specifies revocation independently of the current status of authorization. Some of the aspects relating to the implementation of a system providing independent revocation were discussed. Revocation is first discussed in terms of formal models of authorization. The concept of an access matrix is introduced, and extended to allow for the specification of a condition for database systems. Then the general idea of independent revocation is considered in terms of this extended access matrix. Second, an actual implementation of a system which provides independent revocation is presented. The system, RRDS (Relational Replicated Database System) provides a DISALLOW command which gives the authorizer the capability to specify the data that a user should not be allowed to access. Finally, the applicability of independent revocation to database system in general is explored. It is concluded that independent revocation is applicable to a variety of systems, including some major systems currently in existence.<<ETX>>

Application of SLAM in the design and performance analysis of multi-processor database system

Abstract The software-oriented, multi-processor database systems are characterized by a set of processing elements (PEs) which run identical software and operate on a partitioned database in parallel. Performance improvements and capacity growth can be achieved in this type of system by adding PEs to the configuration and replicating the existing software on the added PEs. Much work has been done applying graph theory, queuing theory, algorithmic approaches, and analytical techniques towards the design of multi-processor database systems. This paper describes a simulation approach and the application of a simulation language, SLAM, to the design and performance analysis of one such multi-processor database system. The system, relational replicated database system (RRDS), was developed using a five-phase design process. Simulation and analytical techniques were used throughout the development to determine critical elements, components, and design issues, and to evaluate proposed solutions. RRDS was modeled as an open queuing system with SLAM service times determined analytically. The model consisted of a workload scenario generator, a query processing module, and a statistics collection module. In phase one of the simulation study, different hardware organizations were evaluated. Results indicated that the RRDS approach performs approximately three times better than other approaches such as SIMD, MIMD, and functional specialization. In phase two, algorithms and mechanisms for data access were developed. Results favored the B + -tree approach over the clustering approach. A data placement strategy was determined in phase three. Results indicated that the value range partitioning (VRP) approach is more desirable than the round-robin (RR) approach. In phase four, a directory management strategy was selected. Results favored a partitioned and parallel-processed directory, as opposed to a rotating approach. Finally, phase five consisted reveal system strengths and weaknesses, and gain insight into optimal RRDS operating environments. This approach to database system design is both iterative and evolutionary, and can be applied regardless of the type of system being considered. Simulation can be a useful tool in all phases of database system design, from the actual physical hardware architecture to the resolution of software design questions. It plays an important role in predictive performance analysis to determine the extent to which original design goals are achieved.

Independent revocation of access rights in database management systems

Abstract The security mechanism of a database management system must provide a means for granting and revoking access to data in the database. In current systems, when an authorizer wants to revoke some access of a user, he must determine how to change the current status of authorization to reflect the revocation. If this is determined incorrectly, the authorization status becomes invalid, and a user may gain improper access to data. It would be preferable if the authorizer were able to simply specify the access that should be revoked, and let the system determine what changes should be made to reflect the revocation. In such a system, the work required by the authorizer is miminized, as is the chance of error. This paper discusses this method of revocation, which we refer to as independent revocation (since the revocation is specified independent of the current status of authorization).