Alfred G. Dale

Indexing Techniques for Object-oriented Databases

Object Oriented Database systems (OODBs) need e cient indexing techniques just like other Database systems. However, B+-trees which work very well for Relational Database systems are not good enough for OODBs. Several alternate indexing techniques have been proposed, amongst them H-trees. This report analyses indexing techniques for OODBs, in particular H-trees.

Cyclic query processing in object-oriented databases

Cyclic query processing issues in object-oriented databases are investigated. A data and cyclic query model is defined for an object-oriented database system, using a graph model. Then the efficient processing of a general object-oriented cyclic query is discussed. For efficient processing, a general cyclic query and the access plans generated for a given query are defined and a cost model is developed to determine the cost for each access plant generated. The retrieval algorithms used for actual data retrieval are also investigated.<<ETX>>

A Parallel Multi-Stage I/O Architecture with Self-Managing Disk Cache ForDatabase Management Applications

This paper first defines and describes a highly parallel external data handling system and then shows how the capabilities of the system can be used to implement a high performance relational data base machine. The elements of the system architecture are an interconnection network which implements both packet routing and circuit switching and which implements data organization functions such as indexing and sort merge and an intelligent memory unit with a self-managing cache which implements associative search and capabilities for application of filtering operations on data streaming to and from storage.

Design of a Hyperkyklos-based Multiprocessor Architecture forHigh-performance Join Operations

The traffic characteristics of various distributed join algorithms on the Hypercube are analyzed. It is shown that, regardless of which join strategy is employed, the network bandwidth requirements of the computation and collection phases are radically different. This imbalance prevents these two phases from being pipelined (overlapped). To alleviate this problem, the HyperKYKLOS Network is proposed. The topology of this network is defined and a brief description of the I/O nodes presently under construction is included.

Database Management Systems Development in the USSR

During the past several years there have been significant developments in the USSR in the utilization of computer-based information processing across all sectors of the Soviet economy and at all levels of its administration. These developments have been supported by the evolution of a thirdgeneration computer hardware and software base and stimulated by an awareness of the critical importance of information processing technology to the functioning of a centrally planned and monitored economy. There is, therefore, a strong impetus to the development of database management system (DBMS) technology to support a broad spectrum of information processing applications. This paper surveys the context within which DBMS developments in the USSR are occurring, examines the features of Soviet DBMS systems reported in the current literature, and reviews current research related to data management software technology. Information from published sources

Data skew and the scalability of parallel joins

When data are uniformly distributed, parallel join algorithms scale up well. However, scalability is curtailed by data skew-nonuniform distribution of data between processors. Investigation of this problem has been hampered by incomplete understanding of data skew as well as inadequate analytic performance models. The authors use a new model of data skew that addresses these shortcomings to examine the effects of skewed workloads on the scalability of the hybrid hash, scheduling hash, and sort-merge parallel join algorithms. Results indicate that the extent to which data skew degrades scalability varies with the join algorithm, the workload and the type of data skew. None of the three algorithms has the best scalability and response time in all cases.<<ETX>>

Main schema-external schema interaction in hierarchically organized data bases

A class of external schemas derivable from a tree structured main schema is identified. It is shown that the properties of this class of schemas permit the construction of a processing interface such that predicates defined on an external schema can be evaluated in an occurrence structure disciplined by the main schema.

File structure determination

An approach to determining an appropriate file structure for a given application is presented, by outlining a methodology for comparing some important aspects of data management system performance. The aspect chosen for analysis is the processing time required to evaluate Boolean functions defined on data values contained within a file structure and select elements from the structure satisfying the expression.Two file structures are studied. The structures are each combinations of hierarchical and inverted file organizations, which differ in the use of the pointers contained in the inverted file. In one case they link a value to nodes corresponding to its occurrence in the data hierarchy and in the second they link a value to the entry which contains the node corresponding to an occurrence.Algorithms for processing within each of the structures are discussed. Each algorithm is then modeled, and approximating models developed for simulation of the algorithms.