Extensions to SQL for historical databases

Abstract

A historical management system (HDBMS) is described which uses an extended relational data model with state-oriented, instead of 'cubic', conceptualization. Two types of historical relations, called state and event relations, are provided for modeling real-world objects. The query language SQL has been extended for definition, retrieval, and update of historical relations. The extended SQL, called HSQL, is a superset of SQL. The author defines a few primitive algebra operations for historical relations, and uses them as a basis for extensions to SQL. In this way, HSQL retains the elegant structural and algebraic framework of SQL. HSQL contains a few new clauses, many operations and built-in functions on time domain, and facilities for retrospective updates and time-rollback.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>