Extant studies of mergers and acquisitions have relied on stock price reactions to evaluate the impact of these events. In this paper, we analyze the performance of the Healy et al. (1992) sample over a ten year period using a managerially controlled efficiency measure, data envelopment analysis (DEA). Our individual firm-level year-by-year analyses results indicate that the managerial performa...

The need to compress data into synopses of summarized information often arises in many application scenarios, where the aim is to retrieve aggregate data efficiently, possibly trading off the computational efficiency with the accuracy of the estimation. A widely used approach for summarizing multidimensional data is the histogram-based representation scheme, which consists in partitioning the d...

Copyright © 2003, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. ABSTRACT In this chapter the author proposes the different approaches for defining operators able to manipulate this multidimensional structure. In particular, he initially considers operators for multidimensional aggregate data which extend relatio...

We investigate the space requirements for summaries needed for maintaining exact answers to aggregate queries over histories of relational databases. We show that, in general, a super-logarithmic lower bound (in the length of the history) on space needed to maintain a summary of the history in order to be able to maintain answers to counting queries. We also develop a natural restriction on the...

Nowadays, we have witnessed the widely recognized phenomenon of high speed data streams. Various statistics computation over data streams is often required by many applications, including processing of relational type queries, data mining and high speed network management. In this paper, we provide survey for three important kinds of aggregate computations over data streams: frequency moment, f...

In many fields and applications, it is critical for users to make decisions through OLAP queries. How to promote accuracy and efficiency while answering multiple aggregate queries, e.g. COUNT, SUM, AVG, MAX, MIN and MEDIAN? It has been the urgent problem in the fields of OLAP and data summarization recently. There have been a few solutions such as MRA-Tree and GENHIST for it. However, they coul...

Accurately estimating the cardinality of aggregate views is crucial for logical and physical design of data warehouses. While the warehouse is under development and data are not available yet, the approaches based on accessing data cannot be adopted. This paper proposes an approach to estimate the cardinality of views based on a-priori information derived from the application domain. We face th...