this paper, some interesting issues related to vertical partitioning in object oriented database systems are presented. A review of existing research is given with an identification of some open problems. A taxonomy of various possible partitioning schemes and a unified view of the vertical partitioning problem are also presented. Existing vertical partitioning algorithms have been studied for their use in both parallel and distributed object-oriented databases

. Vertical partitioning is a useful technique for performance improvement in parallel and distributed object oriented database systems (POBSs and DOBSs). Arising from partitioning, there is a need to modify methods in a user defined schema for correct execution in the partitioned domain. A partitioning scheme should also support application transparency in order to make schema definitions and vertical partitioning independent. We have followed an approach of method transformations for dealing with these problems. A complete taxonomy for the method types arising from vertical partitioning of a class is presented with transformations for each of these types. The role of the transformations in determining the cost of methods is also briefly presented. Keywords Vertical partitioning, Parallel object database, Distributed object database, Object oriented database 1 Introduction The popularity of object oriented database systems (ODBSs) has inspired researchers to find techniques for impro...

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...

In vertically partitioned object oriented database systems, a partitioning scheme should support transparency to applications so that existing applications need not be rewritten. Also the processes of schema design should be independent of partitioning. This can be achieved by transforming methods in a user defined schema for correct execution in the partitioned domain. We present the transformations for hybrid method types which include local complex methods invoking global methods and global complex methods invoking local methods. Keywords Vertical partitioning, Distributed object database, Parallel object database, Object database 1 Introduction Object Oriented Database Systems (ODBSs) evolved out of the need to support non-conventional applications such as office automation systems and CAD. The increasing performance demands from ODBSs inspired researchers for using parallel and distributed processing in these systems. Data partitioning is often used as a means to achieve better...

Abstract. Horizontal fragmentation plays an important role in the design phase of Distributed Databases. Complex class relationships: associations, aggregations and complex methods, require fragmentation algorithms to take into account the new problem dimensions induced by these features of the object oriented models. We propose in this paper a new method for horizontal partitioning of classes with complex attributes and methods, using AI clustering techniques. We provide quality and performance evaluations using a partition evaluator function and we prove that fragmentation methods handling complex interclass links produce better results than those ignoring these aspects. 1.

Abstract:- Class fragmentation is an essential phase in the design of Distributed Object Oriented Databases (DOODB). Due to their semantic similarity with the purpose of database fragmentation (obtaining sets of similar objects with respect to the user applications running in the system), clustering algorithms have recently begun to be investigated in the process of database fragmentation. This work proposes a study on the impact of different similarity measures applied in hierarchical agglomerative clustering algorithms for horizontal fragmentation of classes with complex attributes. This study would eventually help finding formal, automatic, approaches in choosing a particular similarity measure in accordance with: the applied clustering algorithm, the structure of the database inheritance/aggregation hierarchies, the semantics of data, etc. Key-Words:- Distributed database design, horizontal fragmentation, data mining methods, performance evaluation. As opposed to centralized databases where the design phase handles only logical and physical data modeling, the design process in Distributed Object Oriented Databases involves both data partitioning

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...

Vertical partitioning is a technique for reducing the number disk accesses to execute a query by minimizing the number of irrelevant instance variables accessed. The complexity of object-oriented database (OODBs) models due to subclass hierarchy and class composition hierarchy complicates the definition and representation of vertical partitioning of the classes. Furthermore, as the data in the OODB is directly accessed by the encapsulated methods, there is a need to obtain the cost of executing methods for evaluating the utility of vertical class partitioning. In this paper, we develop a cost model for method execution, introduce three algorithms to perform vertical class partitioning (namely, affinity-based, cost-based, and mixed), and show that the mixed approach is not only efficient but also provides mostly optimal (otherwise, near-optimal) vertical class partitioning scheme. KEYWORDS: Vertical partitioning, class partitioning, object-oriented databases, method-induced partitioning...