ANSI X3H2-96-501r2 I S O INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION

This change proposal speci es the addition of tables with valid-time support into SQL/Temporal, and explains how to use these facilities to migrate smoothly from a conventional relational system to a temporal system. Initially, important requirements to a temporal system that may facilitate such a transition are motivated and discussed. The proposal then describes the language additions necessary to add valid-time support to SQL3 while ful lling these requirements. The constructs of the language are divided into four levels, with each level adding increased temporal functionality to its predecessor. The proposal formally de nes the semantics of the query language by providing a denotational semantics mapping to well-de ned algebraic expressions. Several alternatives for implementing the language constructs are listed. A prototype system implementing these constructs on top of a conventional DBMS is publicly available. References [1] Bohlen, M. H. and Marti R.On the Completeness of Temporal Database Query Languages, in Proceedings of the First International Conference on Temporal Logic. D. M. Gabbay and H. J. Ohlbach, eds. Lecture Notes in Arti cial Intelligence 827. Springer-Verlag, July 1994, pp. 283-300. [2] Bohlen, M. H. Valid-Time Integrity Constraints, Aalborg University, October, 1995, 21 pages. [3] Bohlen, M. H., C. S. Jensen and R. T. Snodgrass. Evaluating the Completeness of TSQL2, in Proceedings of the VLDB International Workshop on Temporal Databases. Ed. J. Cli ord and A. Tuzhilin. VLDB. Springer Verlag, Sep. 1995. [4] Cli ord, J., A. Croker and A. Tuzhilin. On Completeness of Historical Relational Query Languages. ACM Transactions on Database Systems, 19, No. 1, Mar. 1994, pp. 64{116. [5] Jackson, M. A. System Development. Prentice-Hall International Series in Computer Science. PrenticeHall International, Inc., 1983. [6] Jensen, C. S. and R. Snodgrass. Temporal Specialization and Generalization. IEEE Transactions on Knowledge and Data Engineering, 6, No. 6 (1994), pp. 954{974. [7] Melton, J. (ed.) SQL/Foundation. July, 1996. (ISO/IEC JTC 1/SC 21/WG 3 DBL-MCI-007.) [8] Melton, J. (ed.) SQL/Temporal. July, 1996. (ISO/IEC JTC 1/SC 21/WG 3 DBL-MCI-0012.) [9] Schueler, B. Update Reconsidered, in Architecture and Models in Data Base Management Systems. Ed. G. M. Nijssen. North Holland Publishing Co., 1977. [10] Snodgrass, R. T., S. Gomez and E. McKenzie. Aggregates in the Temporal Query Language TQuel. IEEE Transactions on Knowledge and Data Engineering, 5, Oct. 1993, pp. 826{842. [11] Snodgrass, R. T. and H. Kucera. Rationale for Temporal Support in SQL3. 1994. (ISO/IEC JTC1/SC21/WG3 DBL SOU-177, SQL/MM SOU-02.) [12] Snodgrass, R. T., K. Kulkarni, H. Kucera and N. Mattos. Proposal for a new SQL Part|Temporal. 1994. (ISO/IEC JTC1/SC21/WG3 DBL RIO-75, X3H2-94-481.) [13] Snodgrass, R. T. (editor) The Temporal Query Language TSQL2. Kluwer Academic Pub., 1995. [14] Steiner, A. and M. H. Bohlen. The TimeDB Temporal Database Prototype, September, 1995. Available at http://www.iesd.auc.dk/general/DBS/tdb/TimeCenter or at ftp://ftp.cs.arizona.edu/tsql/timecenter/TimeDB.tar.gz. [15] Tsichritzis, D.C. and F.H. Lochovsky. Data Models. Software Series. Prentice-Hall, 1982. [16] Yourdon, E. Managing the System Life Cycle. Yourdon Press, 1982. DBL:? and X3H2-96-501r2 3 \Be liberal with ideas, but conservative about their execution." (Presper Eckert, 1919{1995)