Object-oriented database systems (OODBs) need efficient support for manipulation of complex objects. In particular, support of queries involving evaluations of set predicates is often required in handling complex objects. In this paper, we propose a scheme to apply signature file techniques, which were originally invented for text retrieval, to the support of set value accesses, and quantitatively evaluate their potential capabilities. Two signature file organizations, the sequential signature file and the bitsliced signature file, are considered and their performance is compared with that of the nested index for queries involving the set inclusion operator (`). We develop a detailed cost model and present analytical results clarifying their retrieval, storage, and update costs. Our analysis shows that the bitsliced signature file is a very promising set access facility in OODBs. 1 INTRODUCTION Advanced database application areas, such as computer aided design, office automation, and...

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Object-oriented databases (OODBs) are believed to more naturally reflect the behavior and organization of complex application domains. The schema consists of a collection of classes, organized into hierarchies which nicely organize abstractions over the domain. Objects are created as instances of classes, encapsulating data and interpretation of data together. An important characteristic is the support for evolutionary programming, and so that existing programs may be extended with new classes without affecting other parts of the system.

A workshop on temporal relations in Geographic Information Systems (GIS) was held on October 12-13, 1990, at the University of Maine. The meeting was sponsored by the National Center for Geographic Information and Analysis (NCGIA). Seventeen specialists gathered from the fields of Geography, GIS, and Computer Science to discuss users' requirements of temporal GIS and to identify the research issues posed by these requirements. We found - Two paradigms of time as users understand it: one that sees time as a continuum, in which evolution is gradual and often described by differential equations, and another in which time is a sequence of intervals and changes are caused by events. - The need for including exploratory mechanisms appropriate for searches in large datasets. - The convenience of including views that reflect a user's need e.g., temporal/spatial aggregation, and rules to construct these views and to enforce consistency. - The need for the manipulation of inexact or approximate ...

Secondary memory storage plays a major role in making large knowledge bases usable. This paper presents such a storage architecture for knowledge bases. In particular, the Controlled Decomposition Model, a flexible storage model which takes into account the numerous and expressive features of the knowledge representation model is defined. Second, the indexing problem for the knowledge base context is examined and the Temporal Join Index is proposed. An implementation technique for temporal indices, based on a spatial access method, is presented. Finally, an analytical and experimental performance study is conducted to account the performance limits of the proposed methods. 1 Introduction The performance of knowledge base systems slows down significantly as the size of the employed knowledge base increases, if the knowledge base is stored in primary memory. Performance deterioration is even worse when the size of the knowledge base grows much beyond the size of the available main memo...

We investigate clustering techniques that are specifically tailored for object-oriented database systems. Unlike traditional database systems object-oriented data models incorporate the application behavior in the form of type-associated operations. This source of information is exploited for clustering decisions by statically determining the operations' access behavior applying dataflow analysis techniques. This process yields a set of weighted access paths. The statically extracted (syntactical) access patterns are then matched with the actual object net. Thereby the interobject reference chains that are likely being traversed in the database applications accumulate correspondingly high weights. The object net can then be viewed as a weighted graph whose nodes correspond to objects and whose edges are weighted inter-object references. We then employ a newly developed (greedy) heuristics for graph partitioning---which exhibits moderate complexity and, thus, is applicable t...

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Allocation of rules to sites in a distributed deductive database system is an important and challenging task especially for a large knowledge base. We identify communication cost in rule execution to be the primary basis for decomposing a global knowledge base into clusters for their allocation to sites. We show that the problem of optimal allocation is a 0-1 quadratic programming problem, which has prohibitive execution times for large knowledge bases. We propose an efficient heuristic algorithm for rule allocation and study its performance experimentally. We represent a knowledge base as a hierarchy and characterize it in terms of height and inherent clusters with overlaps. The experimental results of the heuristic algorithm on random hierarchies as well as on hierarchies with varying heights and overlaps are seen to be close to the optimal solution. Keywords: Deductive databases, Distributed database systems, Clustering, Quadratic programming. 1 1

The success and acceptance of reuse tools and libraries depends on their integration into existing software development environments. However, the addition of large libraries of reusable components to software design databases only exacerbates the problem of design data management. Object-oriented databases originated to meet the requirements of design data management that relational databases could not satisfy. This paper describes a semantic data model for an object-oriented database supporting an integrated Computer Aided Software Engineering environment (CASE). The data model promotes reuse by providing objects that match program design requirements to existing components in the reuse library. 1 Keywords: Software reuse, Computer-Aided Software Engineering, CASE, Semantic data modelling, Object-Oriented Database Systems. 1.0 Overview To successfully insert reuse into the software development process, we must integrate support for reuse into existing software tools and CASE environ...

The main motivation for the development of a query algebra of complex objects QAL is the study of the operations needed to query the structural aspects of object-oriented databases which are due to the advantages of the object-oriented database model over conventional relational and functional database models. The basic operations of the QAL query algebra evolved from relational algebras and the FQL family of functional query languages by re#ning their operations for the manipulation of objects. In order to support the features speci#c to object-oriented data models, QAL o#ers: #i# a set of operations which provide the means for querying conceptual schemata, and #ii# an operation which provides a simple and e#cientway of querying nested components of complex objects. We show through a case-study consisting of a comprehensive set of examples how these operations can be employed to express a class of queries speci#c to object-oriented databases. Index terms: Database algebras, ...