Representing and Integrating Multiple Calendars

Whenever humans refer to time, they do so with respect to a specific underlying calendar. So do most software applications. However, most theoretical models of time refer to time with respect to the integers (or reals). Thus, there is a mismatch between the theory and the application of temporal reasoning. To lessen this gap, we propose a formal, theoretical definition of a calendar and show how one may specify dates, time points, time intervals, as well as sets of time points, in terms of constraints with respect to a given calendar. Furthermore, when multiple applications using different calendars wish to work together, there is a need to integrate those calendars together into a single, unified calendar. We show how this can be done. (Also cross-referenced as UMIACS-TR-97-12

Probabilistic Temporal Databases, II: Calculus and Query Processing

There is a vast class of applications in which we know that a certain event occurred, but do not know exactly when it occurred. However, as studied by Dyreson and Snodgrass \cite{ds98}, there are many natural scenarios where probability distributions exist and quantify this uncertainty. Dekhtyar et. al. extended Dyreson and Snodgrass's work and defined an extension of the relational algebra to handle such data. The first contribution of this paper is a declarative temporal probabilistic (TP for short) calculus which we show is equivalent in expressive power to the temporal probabilistic algebra of Dekhtyar et. al. Our second major contribution is a set of equivalence and containment results for the TP-algebra. Our third contribution is the development of cost models that may be used to estimate the cost of TP-algebra operations. Our fourth contribution is an experimental evaluation of the accuracy of our cost models and the use of the equivalence results as rewrite rules for optimizing queries by using an implementation of TP-databases on top of ODBC. (Also referenced as UMIACS-TR-2001-79

Tauzaman A system for supporting multiple calendars on the web

The goal of the Tauzaman project is to build a native Java system for formatting and manipulating times and dates in multiple calendars and languages