A database model for object dynamics.

Object-oriented database systems, Dynamic object re-classification, Object role model, Dynamic class hierarchy, Object migration

Prefetching techniques for client server object-oriented database systems

The performance of many object-oriented database applications suffers from the page fetch latency which is determined by the expense of disk access. In this work we suggest several prefetching techniques to avoid, or at least to reduce, page fetch latency. In practice no prediction technique is perfect and no prefetching technique can entirely eliminate delay due to page fetch latency. Therefore we are interested in the trade-off between the level of accuracy required for obtaining good results in terms of elapsed time reduction and the processing overhead needed to achieve this level of accuracy. If prefetching accuracy is high then the total elapsed time of an application can be reduced significantly otherwise if the prefetching accuracy is low, many incorrect pages are prefetched and the extra load on the client, network, server and disks decreases the whole system performance. Access pattern of object-oriented databases are often complex and usually hard to predict accurately. The ..

Evolution of Object-Oriented Database Systems

Data bases are quintessential part of most modern web and mobile applications. In most part, relational databases dominate the database market but the evolution of object-oriented databases has provided users and developers with an alternative option. Object-oriented databases provide a number of advantages over relational databases like ease of extensibility, custom data models, provision for modelling complex data structures and faster access time. But they do lack in certain areas and have no strict standards and implementation mostly depends upon the vendor. Nevertheless, object-oriented databases are slowly finding their way into database market, especially in the area of large-scale databases. But the long history of relational databases keeps them alive as tough competitor and the future seems to be going towards object-relational databases

Performance Evaluation for Clustering Algorithms in Object-Oriented Database Systems

International audienceIt is widely acknowledged that good object clustering is critical to the performance of object-oriented databases. However, object clustering always involves some kind of overhead for the system. The aim of this paper is to propose a modelling methodology in order to evaluate the performances of different clustering policies. This methodology has been used to compare the performances of three clustering algorithms found in the literature (Cactis, CK and ORION) that we considered representative of the current research in the field of object clustering. The actual performance evaluation was performed using simulation. Simulation experiments we performed showed that the Cactis algorithm is better than the ORION algorithm and that the CK algorithm totally outperforms both other algorithms in terms of response time and clustering overhead

Versions and configurations in object-oriented database systems : a uniform treatment

Object-oriented database models usually allow versions only at the most specialized type/c1ass in an inheritance hierarchy. The possibility of having versions at different levels of abstraction provides a richer model and allows a more natural representation of the reality. The presence of objects and its corresponding sets of versions at different levels of a type/class hierarchy introduces the need for handling version mappings. Integrity constraints can be associated to these mappings, restricting the set of possible combinations of versions appearing at different levels of the hierarchy. Sets of versions associated with each levei of an object hierarchy often represent a very large set of possible configurations for that object, which is difficult to be handled directly by the user. In this context, adequate mechanisms are very important to define and build object configurations by means of selections applied to the set of all possible configurations, defined by the combinations of versions. This paper proposes an approach in which versions and configurations may appear at different levels of an inheritance hierarchy, and a uniform treatment is given to these two concepts