Time interval;Time distance

A span is a directed duration of time. A duration is an amount of time with known length, but no specific starting or ending instants. For example, the duration “1 week” is known to have a length of 7 days, but can refer to any block of seven consecutive days. A span is either positive, denoting forward motion of time, or negative, denoting backwards motion in time.

Concerning the synonyms, the terms “time interval” is generally understood to denote an anchored span in the general community of computer science. Only in the SQL language does “time interval” denote a span. The term “span,” which has only one definition, is thus recommended over “time interval” for works not related to the SQL language. This use is unambiguous.

A “duration” is generally considered to be non-directional, i.e., always positive. The term “time distance” is precise, but is longer.

Fixed Span

Temporal Database

Time Instant...

Authors and Affiliations

1. Aalborg University, Aalborg, Denmark

   Christian S. Jensen

2. University of Arizona, Tuscon, AZ, USA

   Richard T. Snodgrass

Editors and Affiliations

1. College of Computing, Georgia Institute of Technology, 266 Ferst Drive, 30332-0765, Atlanta, GA, USA

   LING LIU (Professor) (Professor)

2. Database Research Group David R. Cheriton School of Computer Science, University of Waterloo, 200 University Avenue West, N2L 3G1, Waterloo, ON, Canada

   M. TAMER ÖZSU (Professor and Director, University Research Chair) (Professor and Director, University Research Chair)

Reprints and permissions

© 2009 Springer Science+Business Media, LLC

Policies and ethics