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@inproceedings{DBLP:conf/sigmod/WangJS93,
author = {Xiaoyang Sean Wang and
Sushil Jajodia and
V. S. Subrahmanian},
editor = {Peter Buneman and
Sushil Jajodia},
title = {Temporal Modules: An Approach Toward Federated Temporal Databases},
booktitle = {Proceedings of the 1993 ACM SIGMOD International Conference on
Management of Data, Washington, D.C., May 26-28, 1993},
publisher = {ACM Press},
year = {1993},
pages = {227-236},
ee = {http://doi.acm.org/10.1145/170035.170074, db/conf/sigmod/WangJS93.html},
crossref = {DBLP:conf/sigmod/93},
bibsource = {DBLP, http://dblp.uni-trier.de}
}
In a federated database environment, different constituents of the federation may use different temporal models or physical representations for temporal information. This paper introduces a new concept, called a temporal module, to resolve these differences, or mismatches, among the constituents. Intuitively, a temporal module hides the implementation details of a temporal relation by exposing its information only through two windowing functions: The first function associates each time point with a set of tuples and the second function links each tuple to a set of time points. A caIculus-style language is given to form queries on temporal modules.
Temporal modules are then extended to resolve another type of mismatch among the constituents of a federation, namely, the mismatch involving different time units (e.g., month, week and day) used to record temporsd information. Our solution relies on "information conversions" provided by each constituent. Specifically, each temporal module is extended to provide several "windows" to its information, each in terms of a different time unit. The first step to process a query addressed to the federation is to select suitable windows to the underlying temporal modules. In order to facilitate such a process, time units are formally defined and studied. A federated temporal database model and its query language are proposed. The query language is an extension of the above calculus-style language.
Copyright © 1993 by the ACM, Inc., used by permission. Permission to make digital or hard copies is granted provided that copies are not made or distributed for profit or direct commercial advantage, and that copies show this notice on the first page or initial screen of a display along with the full citation.
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SIGMOD Record 22(2),
June 1993