A Federated Information System requires that multiple (often heterogenous) information systems are integrated to the extent that they can share data through views. One issue faced during the construction of federated ...
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ISBN:
(纸本)0909925836
A Federated Information System requires that multiple (often heterogenous) information systems are integrated to the extent that they can share data through views. One issue faced during the construction of federated view schemata is the continuous need to extract metadata from cooperating systems. This is more pressing in the case of federated multimedia systems where needless transfer of large binary objects affects system performance. Where participating systems employ an object-oriented common model to communicate, obtaining metadata is problematic due to the type and complexity of object-oriented metamodels. In the IOMPAR project, we specified and developed a high-level query interface for the ODMG schema repository in order to simplify this task for integration system engineers. This paper describes a schema repository query language which greatly reduces the efforts of integration engineers.
In this paper we present a uniform approach to dynamic relationships in objectorienteddatabases. We present our relationship categorisation based on dividing the object database into three virtual spaces each hostin...
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Parallel relational databases have been successful in providing scalable performance for data intensive applications, and much work has been carried out on query processing techniques in such systems. However, althoug...
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The development of any comprehensive proposal for spatio-temporal databases involves significant extensions to many aspects of a non-spatio-temporal architecture. One aspect that has received less attention than most ...
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The development of techniques for supporting incremental maintenance of materialized views has been an active research area for over twenty years. However, although there has been much research on methods and algorith...
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object-oriented databases (OODBs) are known to be rich in functionality but poor in performance. One of the important factors that affect performance is the physical database design. We developed a methodology for the...
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object-oriented databases (OODBs) are known to be rich in functionality but poor in performance. One of the important factors that affect performance is the physical database design. We developed a methodology for the design of an efficient storage structure of OODB that minimizes the database operating costs. The input for our method is the logical OODB schema and set of user transactions of retrieval and update types. The output of our method is the determination of which instance variables should be inherited from direct and indirect superclasses and stored in which subclasses. We used a genetic algorithm (GA) to solve this intractable problem. The methodology was applied on a university database. Compared to previous storage models, the storage model produced with our methodology showed database performance improvement ranging from 26% to 31%, on the average. Our results demonstrate a cost-effective storage structure design that boosts the operating performance of OODBs. (C) 2001 Published by Elsevier Science B.V.
This paper describes in a formal way a data schema model which introduces temporal and versioning schema features in an object-oriented environment, In our model, the schema is time dependent and the history of the ch...
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This paper describes in a formal way a data schema model which introduces temporal and versioning schema features in an object-oriented environment, In our model, the schema is time dependent and the history of the changes which occur on its elements are kept into version hierarchies. A fundamental assumption behind our approach is that a new schema specification should not define a new database, so that previous schema definitions are considered as alternative design specifications, and consequently, existing data can be accessed in a consistent way using any of the defined schemas. (C) 2001 Elsevier Science Ltd. All rights reserved.
Relationships have been repeatedly identified as an important object-oriented modeling construct. Most emerging modeling standards such as the object database management group (ODMG) object model and UML have some sup...
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Relationships have been repeatedly identified as an important object-oriented modeling construct. Most emerging modeling standards such as the object database management group (ODMG) object model and UML have some support for relationships. However object-oriented database (OODB) systems have largely ignored the existence of relationships during schema evolution. We are the first to propose comprehensive support for relationship evolution. A complete schema evolution facility for any OODB system must provide primitives to manipulate all object model constructs, and maintenance strategies for the structural and referential integrity of the database under such evolution. We propose a set of basic evolution primitives for relationships as well as a compound set of changes that can be applied to the same. However, given the myriad of possible change semantics a user may desire in the future, any predefined set is not sufficient. Rather we present a flexible schema evolution framework that allows the user to define new relationship transformations as well as to extend existing ones. Addressing the second problem, namely of updating schema evolution primitives to conform to the new set of invariants, can be a very expensive re-engineering effort. In this paper we present an approach that de-couples the constraints from the schema evolution code, thereby enabling their update without any re-coding effort. We also present an approach that can be used to verify the correctness of these complex evolution operations using the de-coupled constraints. (C) 2001 Published by Elsevier Science B.V.
Compensation plays an important role in advanced transaction models, cooperative work and workflow systems. A schema designer is typically required to supply for each transaction T another transaction T-1 to semantica...
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Compensation plays an important role in advanced transaction models, cooperative work and workflow systems. A schema designer is typically required to supply for each transaction T another transaction T-1 to semantically undo the effects of T. Little attention has been paid to the verification of the desirable properties of such operations, however. This paper demonstrates the use of a higher-order logic theorem prover for verifying that compensating transactions return a database to its original state. It is shown how an OODB schema is translated to the language of the theorem prover so that proofs can be performed on the compensating transactions. Copyright (C) 2001 John Wiley & Sons, Ltd.
In this paper, the partitioning/allocation model and algorithm for mapping object-oriented (OO) applications into the heterogeneous distributed environments are proposed. Our model applies the graph-theoretic approach...
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In this paper, the partitioning/allocation model and algorithm for mapping object-oriented (OO) applications into the heterogeneous distributed environments are proposed. Our model applies the graph-theoretic approach, dealing with a lot of characteristics of OO paradigm. In addition, individual metrics for communication cost, concurrency and load balance are defined. Our allocation algorithm is based on the Niched Pareto Genetic Algorithm (NPGA). The reason for using this technique is that a partitioning/allocation problem is multiobjective problem with non-commensurable (measured in different unit) objectives, and NPGA was proved to be effective in this kind of problem. We validated our model and algorithm by experimenting on the three typical OO systems in CORBA-based distributed environments. The main advantage of this approach is that the algorithm produces not a single solution, but a family of solutions known as the Pareto-optimal set, out of which the developer can select an optimal solution appropriate for his or her environmental conditions.
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