Ezeife, C., & Barker, K. (1995). A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Int'l Journal of Distributed and Parallel Databases, 3(3), Kluwer Academic Publishers, pp. 247-272.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....of a relation is performed using predicates that are defined on that relation. On the other hand, derived HP is the partitioning of a relation that results from predicates defined on another relation. A lot of work has been done on the partitioning in the relational models [59] and object models [15, 9, 27, 7] compared to the data warehouses. In this chapter, we will concentrate on HP because it is well adapted to data warehouses. Also, the TPC D benchmark [60] in its implementation allows the utilization of HP, but it discards the utilization of the vertical partitioning. 3.3 Horizontal Partitioning ....

....HP because it is well adapted to data warehouses. Also, the TPC D benchmark [60] in its implementation allows the utilization of HP, but it discards the utilization of the vertical partitioning. 3. 3 Horizontal Partitioning Algorithms in Databases Several algorithms were proposed in performing HP [17, 54, 56, 55, 59, 15, 27, 26]. These algorithms can be classified into two main categories: 1) query driven algorithms and (2) datadriven algorithms. 3.3.1 Query Driven Algorithms These algorithms are performed based on a set of most frequently asked queries and their access frequencies for a specific application [55] ....

[Article contains additional citation context not shown here]

C. I. Ezeife and K. Barker. A comprehensive approach to horizontal class fragmentation in distributed object based system. International Journal of Distributed and Parallel Databases, 3(3):247--272, 1995.

....mechanisms, configurable concurrent control, and others, which compromises the OODBMS performance, as well as its portability. Besides, features such as distribution and parallelism have not yet been well studied in these systems. These features are very important for improving OODBMSs performance [22]. Therefore, one could try to reduce these problems through the use of an open object manager that might be configured with only those features that are necessary in its context of use. An example of this is the Shore system[24] Based on this premise, we decided to use the structure of a ....

Ezeife, C.; Barker, K. - A comprehensive approach to horizontal class fragmentation in distributed object base system - Distributed and Parallel Databases, Kluwer Academic Publishers, 1995

....evaluate query execution time in horizontally fragmented databases. The fragmentation schema with the best performance according to the cost model is achieved through a hill climbing algorithm, by selecting a subset of classes for primary horizontal fragmentation. The work from Ezeife and Barker [7] presents a set of algorithms to the horizontal fragmentation of all classes in a database schema. It takes relationships between classes into account to propose primary and derived horizontal fragmentation. However, this approach works at the instance level, where the class instances already ....

....between classes defined in the method body. For example, we may define a method length( in class AtomicPart as the sum of the attribute length of all its to Connections. e.g.6: select x from x in AtomicPart where x. length( 10 (owner, member) AtomicPart, Connection) Differently from [7], we do not take inheritance relationships (such as the ISA relationship) into account when defining member classes on the database schema. Most object DBMS products do not implement a storage structure for the objects in the database class hierarchy in which an instance of a subclass physically ....

Ezeife, C., Barker, K., "A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System", Int'l Journal of Distributed and Parallel Databases 2(3), 1995, pp.247-272

....gains. Partitioning a large data set across several disks is another way to exploit the I O bandwidth of the disks by reading and writing them in a parallel fashion. User queries have long been adopted for fragmenting a database in the relational, object oriented and deductive database models [Ozsu99, Ezeife95, Lim96]. That is, the set of user queries of a database is indicative of how often the database is accessed and of the portion of the database that is accessed to answer the queries. There are several ways to horizontally partition a relation. Typically, we can assign tuples to processors in a ....

C.I. Ezeife, K. Barker, "A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System", Distributed and Parallel Databases, 1:247-272, 1995.

....It is also possible to perform mixed fragmentation on a class, combining these two techniques. Horizontal fragmentation is usually subdivided in primary and derived fragmentation to address the relationship between entities: the primary horizontal fragmentation is applied on owner entities [10,20], while the derived fragmentation is applied on member entities according to the owner fragmentation. Many researchers [3,10,12,22] have demonstrated the importance of the Design of Distributed Object Oriented Databases (DDOODB) to improve performance of non conventional applications that ....

....is usually subdivided in primary and derived fragmentation to address the relationship between entities: the primary horizontal fragmentation is applied on owner entities [10,20] while the derived fragmentation is applied on member entities according to the owner fragmentation. Many researchers [3,10,12,22] have demonstrated the importance of the Design of Distributed Object Oriented Databases (DDOODB) to improve performance of non conventional applications that manipulate large volumes of data. This is addressed by removing irrelevant data accessed by queries and transactions and by reducing the ....

[Article contains additional citation context not shown here]

EZEIFE, C., BARKER, K., 1995, "A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System", Distributed and Parallel Databases, vol. 3, n 3, pp. 247-272

.... Horizontal fragmentation is usually subdivided in primary and derived fragmentation to address the relationship between entities: primary horizontal fragmentation is applied on owner entities, while derived fragmentation is applied on member entities according to the owner fragmentation [2, 3]. Many researchers have worked on distributed design in the relational model, including [2,4,5] However, in the OO model, the fragmentation process is much more complex than in the relational case. Karlapalem et al. 1] describe the different aspects of a distributed OODBMS that are critical to ....

....of location transparency; and transaction management. The authors also present preliminary ideas to be used in fragmentation algorithms for OO distributed design. In the same way, Maier et al. 6] consider the effect of distribution over complex objects. Also, the works from Ezeife and Barker [3] and Savonnet et al. 7] propose algorithms for horizontal fragmentation of OODBs, while Bellatreche et al. 8] Ezeife and Barker [9] and Malinowski [10] address vertical fragmentation. However, mixed fragmentation is not considered in any of the related works. The semantic differences between ....

[Article contains additional citation context not shown here]

Ezeife, C., Barker, K., "A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System", Distributed and Parallel Databases, 3(3), pp. 247-272, 1995

....3 In this paper, since we do not deal with negation, all the literals in the head and the body of a disjunctive program clause are assumed positive. 3 The Query Based Fragmentation Approach User queries have long been adopted for fragmenting a database in the relational [OV91] object oriented [EB95], and deductive database models [LN96] Since database applications that retrieve and update data from a database are often written as user queries, the set of user queries of a database is indicative of how often the database is accessed and of the portion of the database that is accessed to ....

....are then used as a basis for horizontal fragmentation of relations in D. A minterm predicate is a conjunction of simple (single) predicates where each simple predicate is obtained from a user query. The minterm predicate approach is used by [OV91] for fragmenting a relational database and by [EB95] for fragmenting an object oriented database. However, one of the drawbacks of the minterm predicate approach is that it cannot be adopted to fragment a DDDB since DDDBs allow disjunctive as well as definite facts, whereas the mintermpredicate approach cannot handle disjunctive facts. The ....

[Article contains additional citation context not shown here]

C.I. Ezeife and Ken Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Distributed and Parallel Databases, 3:247--272, 1995.

....query processing such that the answers to each subquery are computed only against those portions of the DDDB relevant to the subquery and can be generated in parallel. The fragmentation algorithms used for the relational model, the object oriented model, and existing deductive database models [5, 7, 1] cannot be adopted directly for a DDDB. For example, assume that a DDDB consists of the ground facts p(a) q(b) and p(b) q(a) By using the partition algorithm of [7] p(a) q(b) forms one fragment and p(b) q(a) forms another. When evaluated against either fragment, the query p(X) q(X) ....

C. I. Ezeife and K. Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Distributed and Parallel Databases, 3:247-- 272, 1995.

....systems are fragmentation and data allocation. Fragmentation allows parallel execution of a single query, reduces the amount of irrelevant data access and unnecessary data transfer, increases the level of concurrency and therefore the system throughput in a distributed database system [6, 14]. Vertical fragmentation further enhances the performance of database transactions by closely matching fragments for the requirements of transactions [12] Our design goals of fragmentation and allocation of rule and data aim to maximize concurrent rule execution, reduce replication of rules and ....

....have been proposed. 13] introduces a vertical partitioning algorithm using a graphical technique that provides an improvement over the previous work on vertical partitioning [12] 10] presents a theory of fragmentation and studies the completeness and update problems of overlapping fragments. [6] develops a fragmentation technique for class objects in a distributed object based system. 11] discusses the rule allocation problem in a distributed database system and proposes a rule partitioning method. 15, 16] construct algorithms for dynamic data allocation in distributed systems. 1] ....

[Article contains additional citation context not shown here]

C. I. Ezeife and K. Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Distributed and Parallel Databases, 3:247--272, 1995.

.... the locality of access of applications because application views are usually subsets of relations [OV91] Because of that fragmentation enhances performance of applications as it reduces the amount of irrelevant data to be accessed and transferred among different sites in a distributed system [EB95]. The decomposition of a relation into fragments also permits concurrent processing since parallel processes created for the same transaction can access fragments of the same relation simultaneously. Fragmentation thus increases the system throughput and decreases the response time of a ....

....expressions and certain knowledge about the data for better estimating user reference clusters. However, their approach, which applies the knowledge to user queries deductively, basically computes the derived horizontal fragmentation that is represented using an extended many sorted language. [EB95] present a set of algorithms for horizontally fragmenting four different class models in a distributed object based system, while [ZZO94] employ a parallel transitive closure algorithm to fragment data in deductive databases. PKV92] on the other hand, propose two strategies for horizontal ....

C. I. Ezeife and K. Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Distributed and Parallel Databases, 3:247--272, 1995.

....It is also possible to perform mixed fragmentation on a class, combining these two techniques. Horizontal fragmentation is usually subdivided in primary and derived fragmentation to address the relationship between entities: the primary horizontal fragmentation is applied on owner entities [9,16], while the derived fragmentation is applied on member entities according to the owner fragmentation. The DDOODB is a very complex task. First, because the semantic differences between relational and OO models inhibit a straightforward migration from existing relational distributed design ....

.... model, including ZSU and VALDURIEZ [16] and NAVATHE et al. 15] In the same way, there are many works demonstrating the importance of the Distributed Design of Object Oriented Databases (DDOODB) to improve performance of non conventional applications that manipulate large volumes of data [3,9,10,17]. However, despite the recent proposals for the DDOODB in the literature, a consensus is far from reachable about what is the best fragmentation technique (vertical, horizontal or mixed) to be applied in each class of the database schema. KARLAPALEM et al. 10] describe different aspects of a ....

[Article contains additional citation context not shown here]

Ezeife, C., Barker, K., 1995, "A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System", Distributed and Parallel Databases, vol. 3, n° 3, pp. 247-272

.... list of benefits of horizontal class partitioning include: 1) different queries access only the needed fragments of a class, so HP will reduce the amount of irrelevant data accessed by queries, 2) HP reduces the amount of data transfered when processing queries across multiple sites distributed [4], 3) the decomposition of a class into horizontal class fragments (HCFs) each being treated as a unit, permits queries to be executed concurrently, and 4) HP can be treated as an objectoriented database schema design technique, which takes a class and generates a class hierarchy of HCFs so as to ....

....4) HP can be treated as an objectoriented database schema design technique, which takes a class and generates a class hierarchy of HCFs so as to increase the efficiency of query execution, while providing additional semantics for the OODB scheme. There has been little work done on the HP in OODBSs [2, 4], in comparison to the relational model [3, 8, 7] Ezeife et al. 4] presented a comprehensive set of algorithms for horizontally partitioning four class models: classes with simple attributes and methods, classes with complex attributes and simple methods, classes with simple attributes and ....

[Article contains additional citation context not shown here]

C. I. Ezeife and K. Barker. A comprehensive approach to horizontal class fragmentation in distributed object based system. International Journal of Distributed and Parallel Databases, 3(3):247--272, 1995.

.... frequently accessed together instances are placed in the same fragment, the number of pages accessed will be reduced [14] Such a partitioning is called Horizontal Partitioning (HP) There is a little work on the HP in OODBSs, in comparison to the relational model, except for the work of [3] [7], 12] and [13] We can not apply the techniques used in the relational model [5] 19] and [18] in a straightforward manner to object oriented models because of the fundamental concepts of an object, that includes features such as encapsulation, inheritance, class composition hierarchy. These ....

....the techniques used in RDBS [16] can be extended to object databases. However, they do not present an effective solution. In [12] and [13] the authors developed representation schemes for horizontal fragmentation, and presented a solution for supporting method transparency in OODBs. Ezeife et al. [7] presented a comprehensive set of algorithms for horizontally fragmenting the four class models. Bellatreche et al. 3] presented two algorithms for generating horizontal class fragments: primary and derived algorithms. The primary algorithm is based on a graph theoretic algorithm [18] developed ....

[Article contains additional citation context not shown here]

C. I. Ezeife and K. Barker. A comprehensive approach to horizontal class fragmentation in distributed object based system. International Journal of Distributed and Parallel Databases, 1, 1995.

....used in relational model [13] can be extended to object databases. However, they do not present an effective solution. In [9, 10] the authors developed representation schemes for horizontal fragmentation, and presented a solution for supporting method transparency in OODBs. Ezeife et al. [8] presented a set of algorithms for horizontally fragmenting the four class models: classes with simple attributes and methods, classes with complex attributes and simple methods, classes with simple attributes and complex methods and classes with complex attributes and methods. They used the ....

C. I. Ezeife and K. Barker. A comprehensive approach to horizontal class fragmentation in distributed object based system. International Journal of Distributed and Parallel Databases, 1, 1995.

....distribution design. As general solution, it proposes the extension of the relational fragmentation methods. Other works present algorithms for fragmenting object oriented databases. We will describe briefly the approach followed in each of the algorithms we know. 1. Ezeife and Barker (1994 1995) [EB94, EB95] have established a taxonomy based on the attribute types (simple or complex) and method types (simple or complex) and have extracted four class models: class model constituted of simple attributes and simple methods, class model constituted of complex attributes and simple methods, class ....

....and simple methods, class attributes constituted of simple attributes and complex methods and last class model constituted of complex attributes and complex methods. Thanks to this classification, they took into consideration , in their algorithms, all the caracteristics of the object orientation. [EB94, EB95] have proposed algorithms for vertical and horizontal fragmentation for each of the class models mentioned above. ffl Horizontal fragmentation The proposed algorithm uses the principle of minterm predicates. Both of the inheritance and aggregation hierarchies are preserved. The principle ....

[Article contains additional citation context not shown here]

C.I. Ezeife and K. Barke. A comprehensive approach to horizontal class fragmentation in distributed object based system. In Distributed and parallel databases, volume 3, pages 247--272. Kluwer Academic Publishers, 1995.

....reduce the amount of irrelevant data accessed by a set of object methods. There has been little work done in devising class based partitioning schemes in object oriented databases. We are aware of one effort conducted by another group, which addresses the same kind of issues of class fragmentation [6, 7]. The approach taken there is to adopt the topdown methodology, taking into account such factors as application access patterns (queries) frequency of queries, object affinity, method and instance variable types, etc. Such an approach is at physical database design level whereas the approach ....

C. I. Ezeife and K. Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System, TR, Dept. of Computer Science, Univ. of Manitoba, 1994

....mechanisms, configurable concurrent control, and others, which compromises the OODBMS performance, as well as its portability. Besides, features such as distribution and parallelism have not yet been well studied in these systems. These features are very important for improving OODBMSs performance [22]. Therefore, one could try to reduce these problems through the use of an open object manager that might be configured with only those features that are necessary in its context of use. An example of this is the Shore system[24] Based on this premise, we decided to use the structure of a flexible ....

Ezeife, C.; Barker, K. - A comprehensive approach to horizontal class fragmentation in distributed object base system - Distributed and Parallel Databases, Kluwer Academic Publishers, 1995

.... fragment, the number of pages accessed can be reduced [15] Such a partitioning is known as horizontal class partitioning (HCP) The HCP is known to reduce the amount of irrelevant data accessed by the queries in both relational databases [7] 22] and [20] and object oriented databases [2] and [9]. Thus, a partial list of benefits of HCP includes: 1) Different queries access or update only the needed fragments of a class, so partitioning will reduce the amount of irrelevant data accessed by the queries, 2) Partitioning reduces the amount of data transferred when processing of distributed ....

.... list of benefits of HCP includes: 1) Different queries access or update only the needed fragments of a class, so partitioning will reduce the amount of irrelevant data accessed by the queries, 2) Partitioning reduces the amount of data transferred when processing of distributed queries is required [9], 3) The decomposition of a class into horizontal class fragments (HCFs) each being treated as a unit, permits queries to be executed concurrently, 4) Further, HCP can be treated as an object oriented database schema design technique [14] which takes a class and generates a class hierarchy of ....

[Article contains additional citation context not shown here]

C. I. Ezeife and K. Barker. A comprehensive approach to horizontal class fragmentation in distributed object based system. International Journal of Distributed and Parallel Databases, 1, 1995.

....the distributed design processes described here. Future research will investigate how these techniques can be incorporated into a dynamic system or determine the amount of change that can be accommodated before a re analysis is required. This paper reviews possible DOBS models presented earlier [3, 4], and contributes by presenting algorithms for vertically fragmenting the class models consisting of (simple attributes, simple methods) complex attributes, simple methods) simple attributes, complex methods) and (complex attributes, complex methods) The balance of the paper is organized as ....

....than one method, so deciding which method group these attributes belong in, so only non overlapping vertical fragments are generated, is required. Two alternative approaches for handling this conflict are: 1) use a set of affinity rules similar to those used in horizontal fragmentation schemes [3] to decide which fragment to place these overlapping attributes or (2) from the onset, group both attributes and methods using attribute method affinity. Approach (1) is preferable for the following performance reasons: a) It drastically reduces the size of the matrices needed by the bond energy ....

C.I. Ezeife and Ken Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. International Journal of Distributed and Parallel Databases, 1, 1995. Kluwer Academic Publishers.

....since more than one application can run on fragments of a class placed at distributed sites concurrently. Fragmentation also reduces data transmission costs by transmitting only part of a class and not the whole class. Recent works on fragmentation of database relations and classes include [3, 4, 8]. All of these earlier distributed database design works are static designs because input to the design process, which include queries accessing database and their frequencies as well as the database schema, are obtained from an earlier full requirements analysis. This implies that when the system ....

....class Person and Student, Student is a subclass of class Person. Object oriented database systems also support class composition and method nesting hierarchies. Each horizontal fragment (C h ) of a class contains all attributes and methods of the class but only some instance objects (I 0 I) [4]. Vertical fragments of a class contain subsets of attributes and methods but all instance objects of the class, while hybrid fragments contain subsets of both attributes, methods and instances of the class. 1.2 Related Work In horizontally fragmenting relations, primary fragmentation is ....

[Article contains additional citation context not shown here]

C.I. Ezeife and Ken Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. International Journal of Distributed and Parallel Databases, 1:247--273, 1995. Kluwer Academic Publishers.

.... Keywords: Object oriented databases, Horizontal fragmentation, Distribution, Performance analysis 1 Introduction The importance of fragmentation of database entities and subsequent allocation to distributed sites (relations or classes) have been argued by many works including [NR89, OV91, EB95, NKR95, BSS96, EB98] All distributed database design work so far in the literature are static because input to the design process, which include queries accessing database and their frequencies as well as the database schema, are obtained from an earlier full requirements analysis. The ....

....system allows a method of a 2 class A that is neither an ancestor class nor a contained (part of) class of another class B to be invoked by methods of class B. Each horizontal fragment (C h ) of a class contains all attributes and methods of the class but only some instance objects (I 0 I) EB95] Vertical fragments of a class contain subsets of attributes and methods but all instance objects of the class, while hybrid fragments contain subsets of both attributes, methods and instances of the class. 1.2 Related Work Ceri, Negri and Pelagatti [CNP82] define application queries in terms ....

[Article contains additional citation context not shown here]

C.I. Ezeife and Ken Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. International Journal of Distributed and Parallel Databases, 1:247--273, 1995. Kluwer Academic Publishers.

....and complex methods. Simple methods are those that do not invoke other methods of other classes. Complex methods are those that can invoke methods of other classes. The classes making up the DOBS are classified based on the nature of the attributes and methods they contain as discussed earlier [5]. Although two basic method types exist, a simple method of a contained (part of) class is referred to as a simple method because it is a simple method of a class that is contained in another class. Thus, the variety of class models that could be defined in a DOBS are: class models consisting of ....

....is feasible [9] However, major changes in a domain would entail a re analysis of the system and re running of the distributed design algorithms. Future research will investigate how these can be incorporated into a dynamic system. This paper reviews possible DOBS models as initially presented in [5], and contributes by presenting algorithms for vertically fragmenting the most complex class model consisting of complex attributes with complex methods. The balance of the paper is organized as follows. We complete this section by briefly reviewing previous work on distributed database design. ....

[Article contains additional citation context not shown here]

C.I. Ezeife and Ken Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. International Journal of Distributed and Parallel Databases, 1, 1995.

....the shared virtual memory manager. To enhance efficiency, the storage manager [41] also provides facilities for accessing generic collections of objects commonly referred to as fragments. Such fragments are constructed using statically derived information on inter object and or class relationships [17, 16, 18] that determine which objects are likely to be accessed concurrently. Related objects are then placed together in a single fragment. The grouping of related objects into fragments allows them to be easily stored in close physical proximity on storage devices. This provides the basis for an ....

C.I. Ezeife and K. Barker. Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. International Journal of Distributed and Parallel Databases, 1(1), 1995.

No context found.

Ezeife, C., & Barker, K. (1995). A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Int'l Journal of Distributed and Parallel Databases, 3(3), Kluwer Academic Publishers, pp. 247-272.

No context found.

C.I. Ezeife and Ken Barker. A Comprehensive Approach to Horizontal Class Fragmentation in a Distributed Object Based System. Distributed and Parallel Databases, 3(3):247--272, 1995.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC