This paper addresses the vertical partitioning of a set of logical records or a relation into fragments. The rationale behind vertical partitioning is to produce fragments, groups of attribute columns, that “closely match ” the requirements of transactions. Vertical partitioning is applied in three contexts: a database stored on devices of a single type, a database stored in different memory levels, and a distributed database. In a two-level memory hierarchy, most transactions should be processed using the fragments in primary memory. In distributed databases, fragment allocation should maximize the amount of local transaction process-ing. Fragments may be nonoverlapping or overlapping. A two-phase approach for the determination of fragments is proposed; in the first phase, the design is driven by empirical objective functions which do not require specific cost information. The second phase performs cost optimization by incorporating the knowledge of a specific application environment. The algorithms presented in this paper have been implemented, and examples of their actual use are shown. 1.

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...

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

The objective of object oriented databases is to respond to the needs of new applications as engineering and multimedia which manipulate complex data. Furthermore, most of these applications need to execute in a distributed environment, making necessary the distribution of data on different sites. This must garantee a minimum cost of inter-site communication and minimum access to irrelevant data. Data distribution has largely been studied in the relational model, but the complex structure of objects and their relationships make it difficult for object oriented databases. In this paper, both fragmentation and allocation problems are tackeled. Hybrid fragments are defined by applying horizontal fragmentation followed by vertical fragmentation to each database class. Resulting fragments are disjoint regarding to data but overlapping regarding to methods. An optimisation model for a nonreplicated data allocation in the form of a non linear integer zero-one programming problem is also develo...

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...

Many researchers have demonstrated the importance of entity fragmentation in distributed relational database design. Database design will be essential in the "next-generation" engineering design environment that exploits object-oriented technologies. 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 have not appeared in the literature. This paper first presents a taxonomy of the fragmentation problem in a distributed object based system capable of supporting systems engineering applications. Detailed horizontal fragmentation algorithms are then presented for one of these class models using a top--down approach where the entity of fragmentation is the class object. The algorithms described i...

This article describes applications of modern heuristic search methods to pattern sequencing problems, i.e., problems seeking for a permutation of the rows of a given matrix with respect to some given objective function. We consider two di#erent objectives: Minimization of the number of simultaneously open stacks and minimization of the average order spread. Both objectives require the adaptive evaluation of changed solutions to allow an e#cient application of neighbourhood search techniques.