Torben Bach Pedersen

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On-line analytical processing (OLAP) systems considerably improve data analysis and are finding wide-spread use. OLAP systems typically employ multidimensional data models to structure their data. This paper identifies 11 modeling requirements for multidimensional data models. These requirements are derived from an assessment of complex data found in(More)
Compressed bitmap indexes are increasingly used for efficiently querying very large and complex databases. The Word Aligned Hybrid (WAH) bitmap compression scheme is commonly recognized as the most efficient compression scheme in terms of CPU efficiency. However, WAH compressed bitmaps use a lot of storage space. This paper presents the Position List Word(More)
On-Line Analytical Processing (OLAP) based on a dimensional view of data is being used increasingly in traditional business applications as well as in applications such as health care for the purpose of analyzing very large amounts of data. Pre-aggregation, the prior materialization of aggregate queries for later use, is an essential technique for ensuring(More)
With the recent and continuing advances in areas such as wireless communications and positioning technologies, mobile, location-based services are becoming possible. % Such services deliver loca\-tion-dependent content to their users. More specifically, these services may capture the movements of their users in multidimensional databases, and their delivery(More)
The efficient analysis of spatio–temporal data, generated by moving objects, is an essential requirement for intelligent location–based services. Spatiotemporal rules can be found by constructing spatio–temporal baskets, from which traditional association rule mining methods can discover spatio–temporal rules. When the items in the baskets are(More)
With wireless communications and geo-positioning being widely available, it becomes possible to offer new e-services that provide mobile users with information about other mobile objects. This paper concerns <i>active, ordered k-nearest neighbor queries</i> for query and data objects that are <i>moving</i> in <i>road networks</i>. Such queries may be of use(More)