Visual Analytics

Abstract

While other temporal aspects have been proposed, such as "decision time" and "event time," closer analysis indicates that the decision and event time of a fact can be captured as either a valid time or a transaction time of some related fact. For example, consider a valid-time Faculty table with attributes Name and Position (i.e., either Assistant Professor, Associate Professor, or Professor) that captures the positions of faculty members. The valid time then captures when a faculty member held a specific position. The "decision time" of a faculty member holding a specific position would be the time the decision was made to hire or promote the faculty member into that position. In fact, there are generally several decision times for a promotion, e.g., recommendation by a departmental promotion and tenure committee, recommendation by a department chair, recommendation by a college promotion and tenure committee, recommendation by a dean, and finally decision by a provost. Each of these decisions may be modeled as a separate fact, with a (event) valid time that captures when that decision was made. The term "valid time" is used widely in the literature and is widely accepted; it is short and easily spelled and pronounced. Most importantly, it is intuitive. Concerning the alternative names, the term "real-world time" derives from the common identification of the modeled reality (opposed to the reality of the model) as the real world. This term is less frequently used. "Intrinsic time" is the opposite of extrinsic time. Choosing intrinsic time for valid time would require one to choose