Vertical Fragmentation Research Articles

Vertical Fragmentation in Databases Using Data-Mining Technique

A new approach to vertical fragmentation in relational databases is proposed using association rules, a data-mining technique. Vertical fragmentation can enhance the performance of database systems by reducing the number of disk accesses needed by transactions. By adapting Apriori algorithm, a design methodology for vertical partitioning is proposed. The heuristic methodology is tested using two real-life databases for various minimum support levels and minimum confidence levels. In the smaller database, the partitioning solution obtained matched the optimal solution using exhaustive enumeration. The application of our method on the larger database resulted in the partitioning solution that has an improvement of 41.05% over unpartitioned solution and took less than a second to produce the solution. We provide future research directions on extending the procedure to distributed and object-oriented database designs.

Prospective closed treatment of nondisplaced and nondislocated condylar neck and head fractures versus open reposition internal fixation of displaced and dislocated fractures

assessment of open reduction internal fixation in displaced or dislocated fractures of the condylar neck and head assessed versus closed treatment of nondisplaced, nondislocated fractures. One hundred and twenty patients suffering from 158 fractures; classes II to V according to Spiessl and Schroll, e.g., displaced and dislocated fractures were operated on; classes I and VI nondisplaced, nondislocated fractures were treated conservatively. At 1year, facial symmetry, pain, facial nerve function, and scarring were assessed clinically; reossification and fragment angulation were assessed from radiographs; vertical position, incisal maximum movements, and condyle translation were judged by millimeters. Clinical courses were uncomplicated in classes I to IV and did reach horizontal and vertical fragment reposition with minor remodeling in follow-up. Single cases evinced persistent pain, dysocclusion, facial nerve palsy, and plate fractures. Results were less successful in classes V and VI: although open reposition internal fixation showed good repositioning in class V, marked vertical bone remodeling occurred; single cases suffered from pain, dysocclusion, and plate fracture. Class VI cases had the worst translation, likewise marked condyle remodeling, and frequent dysocclusion. Classes V and VI remain challenging to treat, while the other classes can be treated reliably with this study's rationale. Condyle remodeling in classes V and VI, translation in class VI may benefit prospectively from even more careful mobilization, improved osteofixation as minimalized operation trauma.

Algorithms for data warehouse design to enhance decision-making

On-line analytical processing (OLAP) queries are strongly affected by the amount data needed to be accessed from the disk. Therefore, there is a need to employ techniques that can facilitate efficient execution of these queries. There has been a lot of work to optimize the performance of relational data warehouses. Among the two fragmentation techniques, vertical fragmentation is often considered more complicated than horizontal, it nearly impossible to obtain an optimal solution. Data partitioning concept that has been studied in the context of relational databases aims to reduce query execution time and facilitate the parallel execution of queries. In this paper, we develop a new framework based on genetic algorithm for applying the partitioning technique on relational DW schema (star schema) to minimize the total query execution cost. We develop an analytical cost model for executing a set of OLAP queries on a partitioned star schema. We conduct experiments to evaluate the utility of partitioning in efficiently executing OLAP queries. Finally, we show how partitioning can be used to facilitate parallel execution of OLAP queries.

Explaining Varieties of Regional Innovation Policies in Europe

Since the 1990s the `region' has been widely acknowledged as an appropriate arena for innovation policies. While regional innovation policies and the creation of regional innovation systems and local clusters are highly propagated by the European Union and the OECD, there are still significant differences in regional activities even among nation states which are equally exposed to global competition, and are similarly dependent on technological innovations, such as Sweden, Switzerland and the Netherlands. The article aims to explain this variation in regional innovation policies by arguing that a country-specific pattern consisting of the geographical concentration of the science and research system, the vertical fragmentation of the political system, the degree of Europeanization, and the endowments of the regions shapes the way innovation policies are pursued in the regions.

Measuring international production fragmentation: where do we stand?

Despite the growing importance of international fragmentation of production, it is still difficult to accurately assess its real size and effect. Several different indicators were proposed over the last decade, but their capacity to provide precise and consistent results is often hindered by the lack of proper data. From an academic and a political standpoint, gaining quantitative knowledge on international vertical fragmentation in production and trade is a major challenge, thus calling for robust and accurate measurement tools. As a first step to face this challenge, this paper takes stock of indicators proposed in the literature, highlighting their advantages and drawbacks and stressing the data requirements.

Fragmentation and East Asia's information technology trade

This article studies the growth and determinants of information technology (IT) trade in the Asia-Pacific region. We argue that the rise of IT trade must be understood within the context of increasing vertical fragmentation of production processes that has occurred over the past two decades. To evaluate this empirically, we estimate a set of pooled bilateral IT export equations for eight Asian countries, the USA and the EU, where foreign direct investment (FDI) inflows are introduced as a proxy for fragmentation. We apply a panel cointegration approach that allows for heterogeneity in short-run dynamics and in fixed effects. Consistent with production fragmentation, we find that the evolution of IT trade can be explained in part by traditional income and relative price effects but also by FDI inflows.

Fragmentation and East Asia's Information Technology Trade

This paper studies the growth and determinants of information technology (IT) trade in the Asia-Pacific region. We argue that the rise of IT trade must be understood within the context of increasing vertical fragmentation of production processes that has occurred over the past two decades. To evaluate this empirically, we estimate a set of pooled bilateral IT export equations for eight Asian countries, the U.S. and the E.U., where FDI inflows are introduced as a proxy for fragmentation. We apply a panel cointegration approach that allows for heterogeneity in short-run dynamics and in fixed effects. Consistent with production fragmentation, we find that the evolution of IT trade can be explained in part by traditional income and relative price effects but also by FDI inflow.

Materialization of fragmented views in multidimensional databases

The most effective technique to enhance performances of multidimensional databases consists in materializing redundant aggregates called views. In the classical approach to materialization, each view includes all and only the measures of the cube it aggregates. In this paper we investigate the benefits of materializing views in vertical fragments, aimed at minimizing the workload response time. We formalize the fragmentation problem as a 0–1 integer linear programming problem, which is then solved by means of a standard integer programming solver to determine the optimal fragmentation for a given workload. Finally, we demonstrate the usefulness of fragmentation by presenting a large set of experimental results based on the TPC-H benchmark.

A Hybrid Fragmentation Approach for Distributed Deductive Database Systems

Fragmentation of base relations in distributed database management systems increases the level of concurrency and therefore system throughput for query processing. Algorithms for horizontal and vertical fragmentation of relations in relational, object-oriented and deductive databases exist; however, hybrid fragmentation techniques based on variable bindings appearing in user queries and query-access-rule dependency are lacking for deductive database systems. In this paper, we propose a hybrid fragmentation approach for distributed deductive database systems. Our approach first considers the horizontal partition of base relations according to the bindings imposed on user queries, and then generates vertical fragments of the horizontally partitioned relations and clusters rules using affinity of attributes and access frequency of queries and rules. The proposed fragmentation technique facilitates the design of distributed deductive database systems.

A Genetic Algorithm for Vertical Fragmentation and Access Path Selection

A Genetic Algorithm for Vertical Fragmentation and Access Path Selection

MIL primitives for querying a fragmented world

In query-intensive database application areas, like decision support and data mining, systems that use vertical fragmentation have a significant performance advantage. In order to support relational or object oriented applications on top of such a fragmented data model, a flexible yet powerful intermediate language is needed. This problem has been successfully tackled in Monet, a modern extensible database kernel developed by our group. We focus on the design choices made in the Monet interpreter language (MIL), its algebraic query language, and outline how its concept of tactical optimization enhances and simplifies the optimization of complex queries. Finally, we summarize the experience gained in Monet by creating a highly efficient implementation of MIL.

Distributed Object Based Design: Vertical Fragmentation of Classes

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 vertically. 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 adopts a classification of classes into four main models, and contributes by proposing algorithms for vertically fragmenting the four realizable class models consisting of simple or complex attributes combined with simple or complex methods. Vertical fragmentation entails splitting classes into a set of “smaller” equivalent classes (actually fragments of the class‘ extent) that can later be placed precisely where they are used. 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 subclasses, its containing classes or its complex method classes.

Vertical fragmentation and allocation in distributed deductive database systems

Although approaches for vertical fragmentation and data allocation have been proposed, algorithms for vertical fragmentation and allocation of data and rules in distributed deductive database systems (DDDBSs) are lacking. In this paper, we present different approaches for vertical fragmentation of relations that are referenced by rules and an allocation strategy for rules and fragments in a DDDBS. The potential advantages of the proposed fragmentation and allocation scheme include maximal locality of query evaluation and minimization of communication cost in a distributed system, in addition to the desirable properties of (vertical) fragmentation and rule allocation as discussed in the literature. We also formulate the mathematical interpretation of the proposed vertical fragmentation and allocation algorithms.

A comprehensive approach to horizontal class fragmentation in a Distributed Object Based System

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 ofrelations 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. Finally, we combine the sets of primary and derived fragments of each class to produce the best possible fragments. Thus, these algorithms account for inheritance and class composition hierarchies as well as method nesting among objects, and are shown to be polynomial time.

A Semantic Approach to Enforce Correctness of Data Distribution Schemes

SQL, the Xplain data language and two entity-relationship approaches have been examined for their usability in the specification of data distribution. It is shown to be difficult to enforce correctness of fragmentation if all possible kinds of fragmentation are allowed. To solve this problem, a new approach to the design of data distribution schemes has been developed. This approach is based on a semantic meta model for fragmentation and allocation with additional restrictions. Only two kinds of horizontal fragmentation are allowed. Vertical fragmentation is not supported, though the possibility of local vertical fragmentation is not excluded

AN EFFICIENT TEST FOR THE VALIDITY OF UNBIASED HYBRID KNOWLEDGE FRAGMENTATION IN DISTRIBUTED DATABASES

Knowledge bases contain specific and general knowledge. In relational database systems, specific knowledge is often represented as a set of relations. The conventional methodologies for centralized database design can be applied to develop a normalized, redundancy-free global schema. Distributed database design involves redundancy removal as well as the distribution design which allows replicated data segments. Thus, distribution design can be viewed as a process on a normalized global schema which produces a collection of fragments of relations from a global database. Clearly, not every fragment of data can be permitted as a relation. In this paper, we clarify and formally discuss three kinds of fragmentations of relational databases, and characterize their features as valid designs, and we introduce a hybrid knowledge fragmentation as the general case. For completeness of presentation, we first show an algorithm for the validity test of vertical fragmentations of normalized relations, and then extend it to the more general case of unbiased fragmentations.

The Vertical Fragment Problem of Clavicle Fractures And Its Surgical Treatment

The Vertical Fragment Problem of Clavicle Fractures And Its Surgical Treatment

Database operating efficiency in fragmented databases in mainframe, mini, and micro system environments

Vertical fragmentation in database design is the process of assigning attributes to physical segments to improve the database performance. Experiments were conducted to measure the performances of four Fragmentation design methods in the three hardware environments with six transaction mixes, using simulation and quantitative modelling. Some hypotheses are laid down regarding database performance and are validated. The MRGB design method which considered the hardware characteristics produced highest fragmentation in micro (IBM AT), and lowest in mini (Prime), with mainframe (IBM) in between. MRGB design performed the best in the three systems. The Hammer & Niamir's design did its best in mini (61%), and better in mainframe (50%) than in mini (41%) in low update environment. While the fully fragmented design performed the best in micro and the worst in mainframe, the unfragmented design performed the best in mini and the worst in micro.

Effect of schema size on fragmentation design in multirelational databases

Vertical fragmentation in database design is aimed at improving database performance. In shared databases, referential integral constraints are maintained to ensure the consistency of database. The database fragment design differences and operating cost differences between large and small databases, in which differential levels of integral constraints exist, are presented. Experiments are conducted with database schema size ranging from 4 to 20 relations with six transaction environments and four fragment design methods. A total of 150 database design problems were solved. Statistically significant optimum design differences between small and large databases were observed. It is shown that the MRGB design is recommended in small and large database fragmentations. The other designs recommended are: unfragmented design in larger databases, trivially fragmented design in smaller databases and Hammer and Niamir's design in large databases with low updates and in smaller databases with medium updates.