Optimal application performance on a Distributed Object Based System (DOBS) requires class fragmentation and the development of allocation schemes to place fragments at distributed sites so data transfer is minimized. Fragmentation enhances application performance by reducing the amount of irrelevant data accessed and the amount of data transferred unnecessarily between distributed sites. Algorithms for effecting horizontal and vertical fragmentation of relations exist, but fragmentation techniques for class objects in a distributed object based system are yet to appear in the literature. This paper first reviews a taxonomy of the fragmentation problem in a distributed object base. The paper then contributes by presenting a comprehensive set of algorithms for horizontally fragmenting the four realizable class models on the taxonomy. The fundamental approach is top--down, where the entity of fragmentation is the class object. Our approach consists of first generating primary horizontal fragments of a class based on only applications accessing this class, and secondly generating derived horizontal fragments of the class arising from primary fragments of its subclasses, its complex attributes (contained classes), and/or its complex methods classes.

. 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...

Processing costs in distributed environments is most often dominated by the network communications required for interprocess communication. It is well-known from distributed relational database design research that careful placement of data "near" the users or processors where it is used is mandatory or system performance will suffer greatly. Data placement in relational database systems is comparatively simple because the data is flat, structured, and passive. Objects are characterized by an inheritance hierarchy (other hierarchies could also be considered including, class composition and execution), unstructured (possibly dynamic data), and contain a behavioral component that defines how the "data" is accessed by encapsulating it within the object per se. Algorithms currently exist for fragmenting relations, but the fragmentation and allocation of objects is still a relatively untouched field of study. Similar to relations, objects can be fragmented both horizontally and ve...

Cooperative Information Systems (CIS) often consist of applications that access shared resources such as databases. Since centralized systems may have a great impact on the system performance, parallel and distribution techniques are need for attaining scalability. Distributed databases are, then, crucial for the development of cooperative applications. However, in order to improve performance, it is very important to design information distribution properly, which is the goal of Distribution Design. Considering the various difficulties embedded in the Design of Distributed Object Oriented Databases, this work presents an algorithm to assist distribution designers in their task. The analysis algorithm indicates the most adequate fragmentation technique (vertical, horizontal or mixed) for each class in the database schema, and we propose the use of a machine learning method - Inductive Logic Programming - to uncover some implicit issues to be considered in the distribution design, thus ...

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 fragmentation may improve the performance of database systems. Defining primary and derived horizontal fragmentation along the classes in a database schema is an important and complex issue, yet not discussed in the literature, which must be considered when horizontally fragmenting a database. In this paper, we focus on an analysis to help the designer upon the decision for primary or derived horizontal fragmentation. This analysis considers performance results of distributed databases using horizontal fragmentation to evaluate the potential benefits and drawbacks of primary and derived techniques. Therefore, this work presents a horizontal fragmentation algorithm that chooses the most adequate strategy (primary or derived) based on class relationships, single class access and query access frequencies 1 Introduction Horizontal fragmentation is often used as a means to achieve better performance of database systems by reducing the disk access required to execute an applicat...

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...

Many object based systems exist that support some form of distribution. Optimal application performance on distributed object based systems demands accurate class fragmentation and the subsequent allocation of these fragments to distributed sites. Vertical fragmentation must minimize application execution time by splitting a class so that all class attributes and methods frequently accessed together are grouped together into a single fragment. This paper describes a fragmentation algorithm that statically creates a set of fragments for the most complex object model: namely, one that supports inheritance and includes a part--of hierarchy, and whose method invocation structure is based on a nested transaction model. Our approach consists of grouping into a fragment, all attributes and methods of the class frequently accessed together by applications running on either this class, its descendant classes, its containing classes or its complex method classes. This research was partially su...

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