Mixed Calendar Query Language Support for Temporal Constants

This proposal represents the rst phase of an ongoing project to add temporal support to a conventional relational query language. We augment the Structured Query Language (SQL) with time values, i.e., temporal constants. The version of SQL we consider is SQL2, the most recent ANSI developed standardization of the language. Our approach is distinct in that we allow many diierent calendars to be used in the database management system, and we incorporate only calendar-independent constructs into the language. The proposal motivates and deenes three new temporal data types. New language features are deened for temporal built-in functions, special time values, arithmetic expressions involving time, temporal predicates, and aggregate functions over time. Semantics and Backus-Naur-Form syntax are provided for all deened constructs. To illustrate the material, we present a comprehensive example of how the particular SQL2 calendar can be implemented within our proposal. MultiCal is in the public domain and you may use it and distribute it in source and binary forms as you wish, provided that this paragraph is duplicated in all forms and that any documentation, advertising materials, and other materials related to such distribution acknowledge that the software was developed at the University of Arizona. The name of the University may not be used to endorse or promote products derived from this software without speciic written permission. This software is provided \as is" and without any express or implied warranties, including, without limitation, the implied warranty of merchantability and tness for a particular purpose. MultiCal is distributed in the hope that it will be useful. We ask that you identify any changes you make. We do intend to continue to develop and maintain the system as resources permit, and would like to hear of any problems.