On the semantics of “now” in databases

Subscribe (Full Service)


	Search: The ACM Digital Library The Guide

	Feedback

On the semantics of “now” in databases

Full text

Pdf (819 KB)

Source

ACM Transactions on Database Systems (TODS) archive
Volume 22 , Issue 2 (June 1997) table of contents

Pages: 171 - 214

Year of Publication: 1997

ISSN:0362-5915

Authors

James Clifford	New York Univ., New York, NY
Curtis Dyreson	James Cook Univ., Townsville, Australia
Tomás Isakowitz	New York Univ., New York, NY
Christian S. Jensen	Aalborg Univ., Aalborg, Denmark
Richard Thomas Snodgrass	Univ. of Arizona, Tucson

Publisher

ACM New York, NY, USA

Bibliometrics

Downloads (6 Weeks): 6, Downloads (12 Months): 80, Citation Count: 31

Additional Information:

abstract references cited by index terms review collaborative colleagues peer to peer

Tools and Actions:	Review this Article Save this Article to a Binder Display Formats: BibTex EndNote ACM Ref

DOI Bookmark:	Use this link to bookmark this Article: http://doi.acm.org/10.1145/249978.249980 What is a DOI?

ABSTRACT

Although “now” is expressed in SQL and CURRENT_TIMESTAMP within queries, this value cannot be stored in the database. How ever, this notion of an ever-increasing current-time value has been reflected in some temporal data models by inclusion of database-resident variables, such as “now” “until-changed, ” “**,” “@,” and “-”. Time variables are very desirable, but their used also leads to a new type of database, consisting of tuples with variables, termed a variable database.

REFERENCES

Note: OCR errors may be found in this Reference List extracted from the full text article. ACM has opted to expose the complete List rather than only correct and linked references.

	1	AL-TAHA, K. K., SNODGRASS, R. T., AND Soo, M.D. 1994. Bibliography on spatiotemporal databases. Int. J. Geograph. Inf. Syst. 8, 1 (Jan.-Feb.), 95-103.
	2	ARIAV, G., BELLER, A., AND MORGAN, H.L. 1984. A temporal data model. Tech. Rep. DS-WP 82-12-05, Decision Sciences Dept., Univ. of Pennsylvania, Dec.
	3	M. A. Bassiouni , M. J. Llewellyn, A relational-calculus query language for historical databases, Computer Languages, v.17 n.3, p.185-197, July 1992 [doi>10.1016/0096-0551(92)90028-L]
	4	Jacov Ben-Zvi, The time relational model, 1982
	5	G. Bhargava , S. K. Gadia, Achieving zero information-loss in a classical database environment, Proceedings of the 15th international conference on Very large data bases, p.217-224, July 1989, Amsterdam, The Netherlands
	6	Vittorio Brusoni , Luca Console , Paolo Terenziani , Barbara Pernici, Extending Temporal Relational Databases to Deal with Imprecise and Qualitative Temporal Information, Proceedings of the International Workshop on Temporal Databases: Recent Advances in Temporal Databases, p.3-22, September 17-18, 1995
	7	James Clifford, Indexical Databases, Advanced Database Systems, p.153-173, January 1993
	8	James Clifford , Albert Croker, The Historical Relational Data Model (HRDM) and Algebra Based on Lifespans, Proceedings of the Third International Conference on Data Engineering, p.528-537, February 03-05, 1987
	9	James Clifford , Albert Croker , Alexander Tuzhilin, On completeness of historical relational query languages, ACM Transactions on Database Systems (TODS), v.19 n.1, p.64-116, March 1994 [doi>10.1145/174638.174642]
	10	CLIFFORD, J., DYRESON, C. E., ISAKOWITZ, T., JENSEN, C. C., AND SNODGRASS, R.T. 1994. On the semantics of'now' in temporal databases. Tech. Rep. R-94-2047, Aalborg Univ., Dept. of Mathematics and Computer Science, Denmark, Nov.
	11	CLIFFORD, g. AND ISAKOWITZ, T. 1993. On the semantics of transaction time and valid time in bitemporal databases. In Proceedings of the ARPA/NSF International Workshop on an Infrastructure for Temporal Databases (Arlington, TX, June), R. T. Snodgrass, Ed., 1.1-I.17.
	12	James Clifford , Tomás Isakowitz, On the semantics of (bi)temporal variable databases, Proceedings of the 4th international conference on extending database technology on Advances in database technology, p.215-230, May 1994, Cambridge, United Kingdom
	13	James Clifford , Abdullah Uz Tansel, On an algebra for historical relational databases: two views, Proceedings of the 1985 ACM SIGMOD international conference on Management of data, p.247-265, May 1985, Austin, Texas, United States
	14	James Clifford , David S. Warren, Formal semantics for time in databases, ACM Transactions on Database Systems (TODS), v.8 n.2, p.214-254, June 1983 [doi>10.1145/319983.319986]
	15	E. F. Codd, A relational model of data for large shared data banks, Communications of the ACM, v.13 n.6, p.377-387, June 1970 [doi>10.1145/362384.362685]
	16	DATE, C. J. AND WHITE, C. J. 1990. A Guide to DB2, Vol. 1, 3rd ed. Addison-Wesley, Reading, MA.
	17	Soumitra Dutta, Generalized Events In Temporal Databases, Proceedings of the Fifth International Conference on Data Engineering, p.118-125, February 06-10, 1989
	18	Curtis Elliott Dyreson, Valid-time indeterminacy, University of Arizona, Tucson, AZ, 1994
	19	Curtis E. Dyreson , Richard Thomas Snodgrass, Timestamp semantics and representation, Information Systems, v.18 n.3, p.143-166, April 1993 [doi>10.1016/0306-4379(93)90034-X]
	20	Curtis E. Dyreson , Richard Thomas Snodgrass, Valid-time Indeterminancy, Proceedings of the Ninth International Conference on Data Engineering, p.335-343, April 19-23, 1993
	21	DYRESON, C. E. AND SNODGRASS, R.T. 1993c. A timestamp representation. In The TSQL Temporal Query Language, R. T. Snodgrass, Ed., Kluwer, Boston, MA, 1995, Chap. 25, 475-499.
	22	Ramez Elmasri , Gene T. J. Wuu , Yeong-Joon Kim, The time index—an access structure for temporal data, Proceedings of the sixteenth international conference on Very large databases, p.1-12, September 1990, Brisbane, Australia
	23	FINGER, M. 1992. Handling database updates in two-dimensional temporal logic. J. Appl. Non-Classical Logics 2, 2.
	24	FRAENKEL, A. A., BAR-HILLEL, Y., AND LEVY, A. 1973. Foundations of Set Theory. North- Holland, Amsterdam, Netherlands.
	25	Shashi K. Gadia, A homogeneous relational model and query languages for temporal databases, ACM Transactions on Database Systems (TODS), v.13 n.4, p.418-448, Dec. 1988 [doi>10.1145/49346.50065]
	26	GADIA, S. AND NAIR, S. 1993. Temporal databases: A prelude to parametric data. In Temporal Databases: Theory, Design, and Implementation, A. Tansel et al., Eds., Benjamin Cummings, Redwood City, CA, Chap. 2, 28-66.
	27	Shashi K. Gadia , Sunil S. Nair , Yiu-Cheong Poon, Incomplete Information in Relational Temporal Databases, Proceedings of the 18th International Conference on Very Large Data Bases, p.395-406, August 23-27, 1992
	28	Christian S. Jensen , Leo Mark, A framework for vacuuming temporal databases, University of Maryland at College Park, College Park, MD, 1990
	29	C. S. Jensen , L. Mark, Queries on Change in an Extended Relational Model, IEEE Transactions on Knowledge and Data Engineering, v.4 n.2, p.192-200, April 1992 [doi>10.1109/69.134258 ]
	30	Christian S. Jensen , Richard Thomas Snodgrass, Temporal Specialization, Proceedings of the Eighth International Conference on Data Engineering, p.594-603, February 03-07, 1992
	31	C. S. Jensen , Richard Thomas Snodgrass, Temporal Specialization and Generalization, IEEE Transactions on Knowledge and Data Engineering, v.6 n.6, p.954-974, December 1994 [doi>10.1109/69.334885 ]
	32	Christian S. Jensen , Richard Thomas Snodgrass, Semantics of time-varying information, Information Systems, v.21 n.4, p.311-352, June 1996 [doi>10.1016/0306-4379(96)00017-8 ]
	33	Curtis Dyreson , Fabio Grandi , Wolfgang Käfer , Nick Kline , Nikos Lorentzos , Yannis Mitsopoulos , Angelo Montanari , Daniel Nonen , Elisa Peressi , Barbara Pernici , John F. Roddick , Nandlal L. Sarda , Maria Rita Scalas , Arie Segev , Richard Thomas Snodgrass , Mike D. Soo , Abdullah Tansel , Paolo Tiberio , Gio Wiederhold, A consensus glossary of temporal database concepts, ACM SIGMOD Record, v.23 n.1, p.52-64, March 1994 [doi>10.1145/181550.181560]
	34	Christian S. Jensen , Michael D. Soo , Richard Thomas Snodgrass, Unifying temporal data models via a conceptual model, Information Systems, v.19 n.7, p.513-547, Oct. 1994 [doi>10.1016/0306-4379(94)90013-2]
	35	Werasak Kurutach , James Franklin, On Temporal-fuzziness in Temporal Fuzzy Databases, Proceedings of the 4th International Conference on Database and Expert Systems Applications, p.154-165, September 06-08, 1993
	36	Witold Lipski, Jr., On semantic issues connected with incomplete information databases, ACM Transactions on Database Systems (TODS), v.4 n.3, p.262-296, Sept. 1979 [doi>10.1145/320083.320088]
	37	N. A. Lorentzos , R. G. Johnson, Extending relational algebra to manipulate temporal data, Information Systems, v.13 n.3, p.289-296, May 1, 1988 [doi>10.1016/0306-4379(88)90040-3]
	38	Jim Melton , Alan R. Simon, Understanding the new SQL: a complete guide, Morgan Kaufmann Publishers Inc., San Francisco, CA, 1993
	39	MONTAGUE, R. 1974. Formal Philosophy: Selected Papers of Richard Montague. Yale University Press, New Haven, CT.
	40	S. B. Navathe , R. Ahmed, A temporal relational model and a query language, Information Sciences: an International Journal, v.49 n.1-3, p.147-175, Oct.-Dec. 1989 [doi>10.1016/0020-0255(89)90026-1]
	41	REITER, R. 1984. Towards a logical reconstruction of relational database theory. In On Conceptual Modelling, Springer Verlag, New York, 191-233.
	42	John F. Roddick, Schema evolution in database systems: an annotated bibliography, ACM SIGMOD Record, v.21 n.4, p.35-40, Dec. 1992 [doi>10.1145/141818.141826]
	43	N. L. Sarda, Algebra and query language for a historical data model, The Computer Journal, v.33 n.1, p.11-18, Feb. 1990 [doi>10.1093/comjnl/33.1.11]
	44	Richard Snodgrass, The temporal query language TQuel, ACM Transactions on Database Systems (TODS), v.12 n.2, p.247-298, June 1987 [doi>10.1145/22952.22956]
	45	SNODGRASS, R.T. 1993. An overview of TQuel. In Temporal Databases: Theory, Design, and Implementation, A. Tansel et al., Eds., Benjamin-Cummings, Redwood City, CA, Chap. 6, 141-182.
	46	Richard Thomas Snodgrass, The TSQL2 Temporal Query Language, Kluwer Academic Publishers, Norwell, MA, 1995
	47	Richard Snodgrass , Ilsoo Ahn, A taxonomy of time databases, Proceedings of the 1985 ACM SIGMOD international conference on Management of data, p.236-246, May 1985, Austin, Texas, United States
	48	SYKES, J. B. (ED.) 1964. The Concise Oxford Dictionary. Oxford University Press, Oxford, England.
	49	A. U. Tansel, Modelling temporal data, Information and Software Technology, v.32 n.8, p.514-520, Oct. 1990 [doi>10.1016/0950-5849(90)90141-D]
	50	Abdullah Uz Tansel , James Clifford , Shashi Gadia , Sushil Jajodia , Arie Segev , Richard Snodgrass, Temporal databases: theory, design, and implementation, Benjamin-Cummings Publishing Co., Inc., Redwood City, CA, 1993
	51	THIRUMALAI, S. AND KRISHNA, S. 1988. Data organization for temporal databases. Tech. Rep., Raman Research Institute, Bangalore, India.
	52	WIEDERHOLD, G., JAJODIA, S., AND LITWIN, W. 1993. Integrating temporal data in a heterogeneous environment. In Temporal Databases: Theory, Design, and Implementation. Benjamin-Cummings, Redwood City, CA, 563-579.
	53	YAU, C. AND CHAT, G. S.W. 1991. TempSQL--A language interface to a temporal relational model. Inf. Sci. Tech. (Oct.), 44-60.

CITED BY 31

	Christian S. Jensen , David B. Lomet, Transaction Timestamping in (Temporal) Databases, Proceedings of the 27th International Conference on Very Large Data Bases, p.441-450, September 11-14, 2001
	Theodoros Tzouramanis , Michael Vassilakopoulos , Yannis Manolopoulos, Benchmarking access methods for time-evolving regional data, Data & Knowledge Engineering, v.49 n.3, p.243-286, June 2004
	Rasa Bliujute , Christian S. Jensen , Simonas Saltenis , Giedrius Slivinskas, R-Tree Based Indexing of Now-Relative Bitemporal Data, Proceedings of the 24rd International Conference on Very Large Data Bases, p.345-356, August 24-27, 1998
	Han-Chieh Wei , Ramez Elmasri, Schema versioning and database conversion techniques for bi-temporal databases, Annals of Mathematics and Artificial Intelligence, v.30 n.1-4, p.23-52, 2000
	Jef Wijsen , Alexis Bès, On query optimization in a temporal SPC algebra, Data & Knowledge Engineering, v.44 n.2, p.165-192, February 2003
	Kristian Torp , Christian S. Jensen , Richard T. Snodgrass, Modification semantics in now-relative databases, Information Systems, v.29 n.8, p.653-683, December 2004
	Bela Stantic , Sankalp Khanna , John Thornton, An efficient method for indexing now-relative bitemporal data, Proceedings of the fifteenth Australasian database conference, p.113-122, January 01, 2004, Dunedin, New Zealand
	Curtis E. Dyreson , Hui-ling Lin , Yingxia Wang, Managing versions of web documents in a transaction-time web server, Proceedings of the 13th international conference on World Wide Web, May 17-20, 2004, New York, NY, USA
	Janne Skyt , Christian S. Jensen , Leo Mark, A foundation for vacuuming temporal databases, Data & Knowledge Engineering, v.44 n.1, p.1-29, January 2003
	Thom McLean , Leo Mark , Margaret Loper , David Rosenbaum, Applying temporal databases to HLA data collection and analysis, Proceedings of the 30th conference on Winter simulation, p.827-834, December 13-16, 1998, Washington, D.C., United States
	Jun Yang , Huacheng C. Ying , Jennifer Widom, TIP: a temporal extension to Informix, ACM SIGMOD Record, v.29 n.2, p.596, June 2000
	Kristian Torp , Christian S. Jensen , Richard Thomas Snodgrass, Effective timestamping in databases, The VLDB Journal — The International Journal on Very Large Data Bases, v.8 n.3-4, p.267-288, February 2000
	Simonas Šaltenis , Christian S. Jensen, Indexing of now-relative spatio-bitemporal data, The VLDB Journal — The International Journal on Very Large Data Bases, v.11 n.1, p.1-16, August 2002
	Jost Enderle , Nicole Schneider , Thomas Seidl, Efficiently processing queries on interval-and-value tuples in relational databases, Proceedings of the 31st international conference on Very large data bases, August 30-September 02, 2005, Trondheim, Norway
	Sabrina De Capitani di Vimercati, An authorization model for temporal XML documents, Proceedings of the 2002 ACM symposium on Applied computing, March 11-14, 2002, Madrid, Spain
	Vedran Mornar , Kresimir Fertalj , Damir Kalpic , Slavko Krajcar, Credit card system for subsidized nourishment of university students, Annals of cases on information technology, Idea Group Publishing, Hershey, PA, 2002
	Curtis E. Dyreson, Temporal coalescing with now granularity, and incomplete information, Proceedings of the 2003 ACM SIGMOD international conference on Management of data, June 09-12, 2003, San Diego, California
	Giedrius Slivinskas , Christian S. Jensen , Richard Thomas Snodgrass, A Foundation for Conventional and Temporal Query Optimization Addressing Duplicates and Ordering, IEEE Transactions on Knowledge and Data Engineering, v.13 n.1, p.21-49, January 2001
	Mohamed F. Mokbel , Walid G. Aref , Susanne E. Hambrusch , Sunil Prabhakar, Towards scalable location-aware services: requirements and research issues, Proceedings of the 11th ACM international symposium on Advances in geographic information systems, p.110-117, November 07-08, 2003, New Orleans, Louisiana, USA
	Curtis E. Dyreson , Richard Thomas Snodgrass, Supporting valid-time indeterminacy, ACM Transactions on Database Systems (TODS), v.23 n.1, p.1-57, March 1998
	Steve Barker, Action-status access control, Proceedings of the 12th ACM symposium on Access control models and technologies, June 20-22, 2007, Sophia Antipolis, France
	Mohamed F. Mokbel , Xiaopeng Xiong , Moustafa A. Hammad , Walid G. Aref, Continuous Query Processing of Spatio-Temporal Data Streams in PLACE, Geoinformatica, v.9 n.4, p.343-365, December 2005
	Justin O'Sullivan , David Edmond , Arthur Ter Hofstede, What's in a Service?, Distributed and Parallel Databases, v.12 n.2-3, p.117-133, September-November 2002
	Michael H. Böhlen , Christian S. Jensen , Richard Thomas Snodgrass, Temporal statement modifiers, ACM Transactions on Database Systems (TODS), v.25 n.4, p.407-456, Dec. 2000
	Fusheng Wang , Carlo Zaniolo, An XML-Based Approach to Publishing and Querying the History of Databases, World Wide Web, v.8 n.3, p.233-259, September 2005
	Janne Skyt , Christian S. Jensen , Torben Bach Pedersen, Specification-based data reduction in dimensional data warehouses, Information Systems, v.33 n.1, p.36-63, March, 2008
	Rodolfo Sabás Gómez , Juan Carlos Augusto, Expressiveness of temporal query languages: on the modelling of intervals, interval relationships and states, Artificial Intelligence Review, v.26 n.4, p.269-289, December 2006
	Mario A. Nascimento , Margaret H. Dunham, Indexing Valid Time Databases via B+-Trees, IEEE Transactions on Knowledge and Data Engineering, v.11 n.6, p.929-947, November 1999
	Fabio Grandi , Federica Mandreoli, A formal model for temporal schema versioning in object-oriented databases, Data & Knowledge Engineering, v.46 n.2, p.123-167, August 2003
	Elisa Bertino , Elena Ferrari , Giovanna Guerrini , Isabella Merlo, T-ODMG: an ODMG compliant temporal object model supporting multiple granularity management, Information Systems, v.28 n.8, p.885-927, December 2003
	Marlon Dumas , Marie-Christine Fauvet , Pierre-Claude Scholl, TEMPOS: A Platform for Developing Temporal Applications on Top of Object DBMS, IEEE Transactions on Knowledge and Data Engineering, v.16 n.3, p.354-374, March 2004

INDEX TERMS

Primary Classification:
H. Information Systems
H.2 DATABASE MANAGEMENT
H.2.3 Languages

Nouns: SQL

General Terms:
Languages, Performance

Keywords:
Now, SQL, TSQL2, indeterminacy, now-relative value, temporal query languge

REVIEW

"Julia E. Hodges : Reviewer"

In many database applications, the ability to represent certain concepts of time, such as “this information is valid now” or “this information is valid until changed, more...

Collaborative Colleagues:

James Clifford: colleagues

Curtis Dyreson: colleagues

Tomás Isakowitz: colleagues

Christian S. Jensen: colleagues

Richard Thomas Snodgrass: colleagues

Peer to Peer - Readers of this Article have also read: