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For similarity search in high-dimensional vector spaces (or 'HDVSs'), researchers have proposed a number of new methods (or adaptations of existing methods) based, in the main, on data-space partitioning. However, the performance of these methods generally degrades as dimensionality increases. Although this phenomenon-known as the 'dimensional curse'-is(More)
Usually, the first normal form condition of the relational model of data is imposed. Presently, a broader class of data base applications like office information systems is considered where this restriction is not convenient. Therefore, an extension of the relational model is proposed consisting of Non First Normal Form (NF<sup>2</sup>) relations. The(More)
New applications like office information systems need interfaces to data bases which integrate classical data manipulation with management and retrieval of textual (" unformatted ") data. The relational data model is widely accepted as a high level interface to classical (" formatted ") data management. It turns out, however, to be inconvenient for handling(More)
While cluster computing is well established, it is not clear how to coordinate clusters consisting of many database components in order to process high workloads. In this paper, we focus on Online Analytical Processing (OLAP) queries, i.e., relatively complex queries whose evaluation tends to be time-consuming, and we report on some observations and(More)
Processes are increasingly being used to make complex application logic explicit. Programming using processes has significant advantages but it poses a difficult problem from the system point of view in that the interactions between processes cannot be controlled using conventional techniques. In terms of recovery, the steps of a process are different from(More)
Data warehouses offer a compromise between freshness of data and query evaluation times. However, a fixed preference ratio between these two variables is too undif-ferentiated. With our approach, clients submit a query together with an explicit freshness limit as a new Quality-of-Service parameter. Our architecture is a cluster of databases. The(More)
This paper describes a new signature generation method for constructing multi-level signature files to support both relational queries which contain multiple conjunctive (AND) predicates and generic document text queries. We describe the major problems with traditional multi-level signature files and then describe how to build multi-level signature files(More)