In this thesis we address the problem of providing efficient processing of queries in the extensible environment induced by object-oriented databases. We define a framework for query processing in an object-oriented database and develop designs for major components of this framework. The framework encompasses an object-oriented data model, an algebra to query over that model, transformation rules for the algebra, an internal representation for queries expressed in the algebra, a cost model for analyzing query expressions, and an architecture for an extensible query optimizer. The major contributions of this thesis are an algebra and transformation rules, a representation, and an architecture for extensible query optimization. We show how these components fit into the framework and interact with each other. The EQUAL query algebra presented in this thesis is the first query algebra for object-oriented database systems to be completely consistent with data abstraction, and one of the few...

Query optimizers for persistent object systems should be extensible to react to user-supplied abstract types. Current architectures support only a single, non-extensible technique for controlling the optimization process. We propose an alternative to the current extensible architectures that will support multiple optimizer control strategies and the addition of new control strategies. The optimizer consists of a collection of optimization regions, each of which can transform queries according to a particular control strategy, set of transformations and cost model. A global optimizer control coordinates the movement of a query between these regions. This architecture provides extensibility in the optimizer's repertoire of control strategies through the addition of new regions. In this paper we describe our approach and demonstrate its utility by following the optimizer as it works on an example query. The optimizer will move the query between three distinct regions. The different region...

Query processors have long been monolithic pieces of software that resist extension. Query capabilities are needed in many applications of persistent object bases, but object models and storage managers are evolving so rapidly that matching a monolithic query processor to each of them is infeasible. The EREQ project seeks to structure object query processors into well-defined software components that can be independently modified, extended and exchanged. This paper sets forth our initial ideas on what the major components will be and how we will specify the interfaces to each. 1 Introduction The EREQ Project 1 is a recently launched effort to devise a common internal architecture for query processing in persistent object bases. A goal of the work is to specify the interfaces to the query optimizer component precisely enough that we can interchange query optimizers between query processing systems. We are conducting our investigations in an object-oriented database setting, ...

In the late 80's new applications such as CAD, hyper-media, and programming environments stressed to the limit existing database technology [2]. To meet the demands of these new domains OODBs were developed. There was, and still is a great diversity in their architecture and functionality. Furthermore, this functionality continues to evolve [14, 22]. However, early on one common feature emerged and that is they all used some distinct service that provided stable storage for objects or pages, referred to as object servers and page servers respectively [13]. This paper describes problems facing the continued development of object stores and addresses them in the design of ObServer2. The design takes a new approach to the construction of an object server that allows it to meet changing needs. Also, it presents original contributions in the design of concurrency control and recovery algorithms. New applications such as CAD, hyper-media, and programming environments stress existing ...

1.1 General Remarks............................ 3

In recent years, a growing demand for non-standard database systems could be observed. CAD systems, geographical, spatial, and spatio-temporal information systems, multimedia applications or management systems for semistructured data typically perform data-intensive operations, offer concurrent access to their data, and provide query capabilities. Implementing them on top of a database management system appears straightforward. Conventional relational systems, however, do not meet the requirements of such applications due to the restrictions of the relational data model. This thesis