There can be no denying, I believe, that insofar as current major Database Management Systems (DBMS) are concerned, temporal data represents a significant problem: it is simply not possible to declaratively constrain the integrity of temporal data in SQL databases (or non-temporal data, even). I am not alone I am sure in having had to deal with duplicate, triplicate, quadruplicate, etc., records covering, or abutting, or overlapping on the same temporal periods. Not to mention the hoops that must be jumped through to reliably manipulate those same data.Date, Darwen, and Lorentzos have produced a formidable work here on applying some badly needed rigid logic to the whole sphere of temporal data within databases. And that rigid logic is afforded by the Relational Model. They consider three variants on the temporal data theme as vehicles for explanation and demonstration: 1. Semitemporal with current data only, 2. Temporal with current and historical data held within the same relvars (tables), 3. Temporal with current and historical data split into separate relvars. Temporal data is a complex area, so this book has, inevitably, had to get 'down and dirty' with the detail, but the authors are clear and comprehensive throughout. A thorough familiarity with the Relational Model will help, as will any previous experience of their Relational language `Tutorial D', though they go though both in the first two introductory chapters.We would indeed be much better off were the DBMS vendors to take serious note of the powerful logical arguments laid forth in this volume, and far from interpreting their reflections (criticisms) on NULLs, etc., as 'political', I would see them only as further reaffirmations of the principles that have led them to invest so much endeavour and thought into the problems and very real deficiencies of data modelling and integrity, specifically in regard to the Relational Model. And for that we should indeed be thankful.
Author(s): C.J. Date, Hugh Darwen, Nikos Lorentzos
Series: The Morgan Kaufmann Series in Data Management Systems
Edition: 1
Publisher: Morgan Kaufmann
Year: 2002
Language: English
Pages: 448
Front Cover......Page 1
Temporal Data and the Relational Model......Page 4
Copyright Page......Page 6
Contents......Page 12
Preface......Page 18
Part I: Preliminaries......Page 24
1.1 Introduction......Page 26
1.2 The Running Example......Page 27
1.3 Types......Page 29
1.4 Relation Values......Page 34
1.5 Relation Variables......Page 39
1.6 Integrity Constraints......Page 44
1.7 Relational Operators......Page 46
1.8 The Relational Model......Page 57
Exercises......Page 58
2.3_ Introduction......Page 62
2.2 Scalar Type Definitions......Page 64
2.3 Relational Definitions......Page 65
2.4 Relational Expressions......Page 66
2.5 Relational Assignments......Page 70
2.6 Constraint Definitions......Page 71
Exercises......Page 72
Part II: Laying the Foundations......Page 74
3.1 Introduction......Page 76
3.2 Timestamped Propositions......Page 79
3.3 Valid Time versus Transaction Time......Page 82
3.4 Some Fundamental Questions......Page 84
Exercises......Page 87
4.1 Introduction......Page 88
4.2 "Semitemporalizing" Suppliers and Shipments......Page 90
4.3 Fully Temporalizing Suppliers and Shipments......Page 93
Exercises......Page 98
5.1 Introduction......Page 100
5.2 Applications of Intervals......Page 103
5.3 Point Types and Interval Types......Page 104
5.4 A More Searching Example......Page 108
Exercises......Page 109
6.1 Introduction......Page 112
6.2 Comparison Operators......Page 114
6.3 Other Operators......Page 116
6.4 Sample Queries......Page 118
Exercises......Page 120
7.1 Introduction......Page 122
7.2 Expanded Form......Page 123
7.3 Collapsed Form......Page 124
7.4 Operating on Sets of Intervals......Page 126
7.5 Treating Sets as Unary Relations......Page 128
7.6 Operating on Nullary Relations......Page 130
Exercises......Page 131
8.1 Introduction......Page 132
8.2 Packing Relations......Page 134
8.3 Unpacking Relations......Page 138
8.4 Sample Queries......Page 143
8.5 Packing and Unpacking on No Attributes......Page 146
8.6 Packing and Unpacking on Several Attributes......Page 147
8.7 Further Points......Page 154
Exercises......Page 161
9.1 Introduction......Page 164
9.2 Union, Intersect, and Difference......Page 165
9.3 Restrict and Project......Page 170
9.4 Join......Page 172
9.5 Extend and Summarize......Page 173
9.6 Group and Ungroup......Page 174
9.7 Relational Comparisons......Page 178
9.8 The Underlying Intuition......Page 179
9.9 The Regular Relational Operators Revisited......Page 181
Exercises......Page 182
Part III: Building on the Foundations......Page 184
10.1 Introduction......Page 186
10.2 Current Relvars Only......Page 189
10.3 Historical Relvars Only......Page 192
10.4 Sixth Normal Form......Page 195
10.5 "The Moving Point Now"......Page 200
10.6 Both Current and Historical Relvars......Page 203
10.7 Concluding Remarks......Page 206
Exercises......Page 207
11.1 Introduction......Page 210
11.2 The Redundancy Problem......Page 214
11.3 The Circumlocution Problem......Page 215
11.4 The Contradiction Problem......Page 217
11.6 PACKED ON without WHEN/THEN......Page 219
11.7 WHEN/THEN without PACKED ON......Page 220
11.8 Neither PACKED ON nor WHEN/THEN......Page 227
11.9 Candidate Keys Revisited......Page 230
11.10 PACKED ON Revisited......Page 233
Exercises......Page 234
12.1 Introduction......Page 236
12.2 The Nine Requirements......Page 237
12.3 Current Relvars Only......Page 239
12.4 Historical Relvars Only......Page 243
12.5 Both Current and Historical Relvars......Page 250
12.6 Syntactic Shorthands......Page 262
12.7 Concluding Remarks......Page 266
Exercises......Page 267
13.1 Introduction......Page 268
13.2 Current Relvars Only......Page 270
13.3 Historical Relvars Only......Page 275
13.4 Both Current and Historical Relvars......Page 279
13.5 Virtual Relvars Can Help......Page 283
Exercise......Page 288
14.1 Introduction......Page 290
14.2 Current Relvars Only......Page 291
14.3 Historical Relvars Only (1)......Page 294
14.4 Historical Relvars Only (II)......Page 306
14.5 Both Current and Historical Relvars......Page 309
14.6 Virtual Relvars Can Help......Page 315
Exercises......Page 318
15.1 Introduction......Page 320
15.2 A Closer Look......Page 322
15.3 The Database and the Log......Page 325
15.4 Terminology......Page 328
15.5 Logged-Time Relvars......Page 331
15.6 Queries Involving Logged-Time Relvars......Page 334
Exercises......Page 335
16.1 Introduction......Page 336
16.2 Type Inheritance......Page 338
16.3 Point Types Revisited......Page 344
16.4 Further Examples......Page 347
16.5 Granularity Revisited......Page 354
16.6 Interval Types Revisited......Page 358
16.7 Cyclic Point Types......Page 360
16.8 Continuous Point Types......Page 367
Exercises......Page 370
APPENDIXES......Page 372
Appendix A. IMPLEMENTATION CONSIDERATIONS......Page 374
Appendix B. GENERALIZING THE EXPAND AND COLLAPSE OPERATORS......Page 406
Appendix C. REFERENCES AND BIBLIOGRAPHY......Page 414
INDEX......Page 434
ABOUT THE AUTHORS......Page 444
