. Horizontal partitioning (HP) technique is a logical database design technique first developed for distributed relational (record structured) databases. Though the main objective of HP is to reduce irrelevant data access, there has been very little work done in quantifying this by means of a cost model, and developing algorithms which derive the horizontal partitioning schemes. In this paper, we develop a cost model for query processing in object oriented databases (OODBs) for both unpartitioned and horizontally partitioned object oriented databases. The problem of coming up optimal HP scheme is NP-complete. Therefore, we present and evaluate two algorithms for coming up with optimal (based on exhaustive search) and/or near optimal (based on heuristics) HP schemes. 1 Introduction OODB technology has matured enough to support modern applications such as CAM/CAD, software engineering and multimedia databases. HP is often used as a means to achieve better performance out of database sys...

Introduction Information is one of the most valuable assets of an organization and when used properly can assist intelligent decision making that can significantly improve the functioning of an organization. Data warehousing is a recent technology that allows information to be easily and efficiently accessed for decision making activities. On-Line Analytical Processing (OLAP) tools are wellstudied for complex data analysis. A data warehouse is a set of subject-oriented, integrated, time varying, and non-volatile databases used to support the decision-making activities [42]. The conceptual architecture of a data warehousing system is shown in Figure 1. The data Information Sources - Relational -Legacy Warehouse Meta Data - Select -Transform -Clean -Integrate -Refresh -Others -Network Data OLAP Server MOLAP ROLAP/ Clients Front-end Tools -Analysis -Data Mining -Report generator - Others and Management Component Warehouse Creation

Horizontal partitioning is a technique for reducing the number of disk accesses to execute a query by minimizing the number of irrelevant instances accessed. In this paper, we develop a cost model for query execution in the case of unpartitioned and horizontally partitioned classes. We present three algorithms to perform horizontal partitioning in OODBSs, namely: Cost-Driven Algorithm(CDA), Predicate Affinity Algorithm (PAA) and Approximate Algorithm. CDA is based on the cost model, that aims to reduce the number of disk accesses for executing a set of queries, and PAA is an extension of the graph theoretic algorithm for a relational model to an OODB model. The Approximate algorithm takes the advantages of both PAA and CDA to facilitate efficient and good horizontal fragmentation scheme design for object-oriented databases. We also evaluate the goodness of horizontal class fragmentation through experiments using an analytical cost model. Finally, horizontal class partitioning could als...

Query processing remains one of the most important challenges of object oriented database systems (OODBSs). A cost model for query processing is very useful in performing the physical query optimization. Horizontal class partitioning (HCP) is a technique for reducing the number of disk accesses for executing a given set of queries by minimizing the number of irrelevant object instances accessed. Moreover, its importance in reduction of query execution time has been widely acknowledged. However, existing cost models for query processing in OODBSs do not take into consideration the HCP criteria. In this paper, we present an analytical cost model for query execution for unpartitioned and horizontally partitioned classes. This cost is necessary for deciding whether to use HCP or to keep all classes unpartitioned. The effect of HCP upon the query execution process is analyzed. Key Words : Object-oriented database, horizontal class partitioning, cost model, query processing, query optimizat...