Darwen Hugh - Time and Relational Theory

1. Figures in Chapter 1
2. Figures in Chapter 2
3. Figures in Chapter 5
4. Figures in Chapter 6
5. Figures in Chapter 9
6. Figures in Chapter 10
7. Figures in Chapter 11
8. Figures in Chapter 13
9. Figures in Chapter 14
10. Figures in Chapter 15
11. Figures in Chapter 16
12. Figures in Chapter 17
13. Figures in Chapter 18
14. Figures in Chapter 19
15. Figures in Appendix A
16. Figures in Appendix C
17. Figures in Appendix E

Second Edition

C. J. Date

Hugh Darwen

Nikos A. Lorentzos

Cover Image: Lords Cricket Ground

Text design: C. J. Date

Acquiring Editor: Steve Elliot

Editorial Project Manager: Kaitlin Herbert

Project Manager: Mohana Natarajan

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ISBN: 978-0-12-800631-3

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The cover illustration is the famous weathervane Old Father Time from Lords Cricket Ground in London.

We would like to dedicate this book to the innocent victims who died on September 11th, 2001, and during the weeks, months, and years thereafter

C. J. Date, Hugh Darwen, Nikos A. Lorentzos

Also to my friends in the Healdsburg Peace Project still keeping the faith after all these years

C. J. Date

And to the memory of my friend Adrian Larner, who had such a huge influence on my database thinking

Hugh Darwen

And to the memory of my father, Antonios

Nikos A. Lorentzos

What, then, is time? I know well enough what it is, provided that nobody asks me; but if I am asked what it is and try to explain, I am baffled.

Saint Augustine of Hippo: Confessions (397)

The distinction between past, present, and future is only a stubbornly persistent illusion.

Albert Einstein: Letter to the family of Michele Besso (1955)

Time is what keeps everything from happening at once.

Ray Cummings: The Girl in the Golden Atom (1922)

Time is what happens when nothing else does.

Richard Feynman (attrib.)

Time present and time past Are both perhaps present in time future, And time future contained in time past.

T. S. Eliot: Burnt Norton (1936)

C.J.Date is an independent author, lecturer, researcher, and consultant, specializing in relational database technology. He is best known for his book An Introduction to Database Systems (8th edition, Addison-Wesley, 2004), which has sold some 900,000 copies at the time of writing and is used by several hundred colleges and universities worldwide. He is also the author or coauthor of numerous other books on database management. He was inducted into the Computing Industry Hall of Fame in 2004. He enjoys a reputation that is second to none for his ability to explain complex technical subjects in a clear and understandable fashion.

Hugh Darwen was employed in IBMs software development divisions from 1967 to 2004. In the early part of his career, he was involved in DBMS development; from 1978 to 1982, he was one of the chief architects of an IBM product called Business System 12, a product that faithfully embraced the principles of the relational model. He was an active participant in the development of the international SQL standard (and related standards) from 1988 to 2004. Based in the U.K., he currently teaches relational database theory at Warwick University and is a tutor and course development consultant for the Open University. He has written two books on database management as well as coauthoring several others with C. J. Date. He has received honorary degrees from the University of Wolverhampton and the Open University.

Nikos A. Lorentzos is a Professor at the Agricultural University of Athens. He is mainly known for his research in temporal (also spatiotemporal) databases. He has participated in relevant European Union funded projects (prime researcher for the development of a temporal DBMS). The temporal model he has proposed has been extensively evaluated by independent researchers with positive comments; it is described in books addressed to university students, it has been the basis of PhDs undertaken in Europe, it has attracted the interest of DBMS developers, and it has had impact on international standards, as witnessed by the fact that SQL:2011 includes temporal characteristics proposed exclusively in his research. He is coeditor of the book Spatiotemporal Databases: The Chorochronos Approach