Abstract
In a federated database environment, different constituents of the federation may use different temporal models or physical representations for the temporal information. This paper introduces a new concept, called a temporal module, to resolve these 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: one function associates each time point to a set of tuples and the other function links each tuple with a set of time points. A calculus-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 in recording temporal information. Our solution to this mismatch relies on "information conversions" provided by each constituent. Specifically, a temporal module is extended to provide several conversion functions; each converts its information to a different time unit. The first step to process a query addressed to the federation is to select suitable conversion functions from the extended temporal modules. In order to do so, 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 calculus-style language above.
Original language | English (US) |
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Pages (from-to) | 103-128 |
Number of pages | 26 |
Journal | Information Sciences |
Volume | 82 |
Issue number | 1-2 |
DOIs | |
State | Published - Jan 1995 |
Externally published | Yes |
Funding
The research of Wang and Jajodia was supported in part by an ARPA grant, administered by the Office of Naval Research under grant number NO01~-92-J-~038. The research of Subrahmanian was supported in part by the Army Research Office under Grant Number DAAL-O3-Y2-G-0225, the Air Force Orifice of Scientific Research under grant number F~9620-93-1-0065 and the National Science Foundation under Grant Number IRI- 9109755.
ASJC Scopus subject areas
- Software
- Control and Systems Engineering
- Theoretical Computer Science
- Computer Science Applications
- Information Systems and Management
- Artificial Intelligence