How can databases evolve to represent enterprises over time? This paper introduces TQuel, a new language for querying temporal databases that offers a minimal extension to Quel, aiming to simplify interaction with data across time. TQuel, designed as an extension of Quel, provides a tuple relational calculus semantics for statements that diverge from their Quel counterparts, including modification statements. The authors focus on how TQuel's additional temporal constructs directly mirror Quel's 'where' clause and target list. The study showcases the reducibility of TQuel's semantics to Quel's when applied to a static database, emphasizing its practicality and efficiency. By extending Quel with temporal constructs, TQuel allows users to query databases representing enterprises over time. The semantics of TQuel are discussed, and it is shown that the additional temporal constructs defined in TQuel are direct semantic analogues of Quel's where clause and target list. TQuel offers a simple and direct approach to interacting with temporal data, potentially enhancing decision-making across a range of industries. Its reducibility to Quel in static databases ensures compatibility and ease of integration, making it a valuable tool for database management and analysis.
Published in ACM Transactions on Database Systems, this research directly addresses the journal’s core audience focused on database management and query languages. The introduction of TQuel, a minimal extension to Quel, aligns with the journal's interest in efficient and practical database solutions. The rigorous formalization of TQuel semantics, including modification statements, exemplifies the journal’s commitment to theoretical depth and rigor.