From info-tsql-sender Mon Jul 5 15:45:31 1993 Date: Mon, 5 Jul 1993 15:32:21 MST From: "Rick Snodgrass" To: tsql@cs.arizona.edu Subject: SQL temporal language extensions Content-Length: 3588 X-Lines: 81 Status: RO One major objective of the temporal database infrastructure workshop (held three weeks ago in Arlington, TX) was to initiate the design of a consensus temporal extension of SQL. There were three conflicting viewpoints on such an extension voiced by the workshop participants (with associated rationales, not repeated here): (a) With the addition of an interval data type, there will be sufficient support in SQL2/3's data model to support applications using temporal data. Further temporal support within the data model should not be added. (b) SQL2, and the proposed SQL3, require temporal support to be added to their data model and query language. A two-pronged effort should be initiated, the first being a short-term effort to define a temporal extension to SQL2 and the second being a long-term effort to define a comprehensive extension to SQL3. (c) Temporal support should be added, but only SQL3 should be extended. These three viewpoints are clearly at variance. So, instead of a single consensual effort, which appears to be unattainable, three separate efforts have been initiated, each reflecting the approach espoused by a significant portion of the TDB community, and together enabling further progress. The following working groups have been started. If you would like to participate in one of these working groups, please contact the group coordinator. * The SQL2/3 working group Those agreeing with viewpoint (a) will define an interval data type and write SQL2 (or SQL3) queries for the benchmark queries, so that this approach can be compared with other proposals. Nikos Lorentzos has volunteered to coordinate this effort. * The TSQL2 working group Those agreeing with viewpoint (b) will define a short-term temporal extension to SQL2. I have volunteered to coordinate this effort. * The TSQL3 working group Those agreeing with viewpoint (b) or with viewpoint (c) will define a long-term temporal extension to SQL3. Gene Wuu has volunteered to coordinate this effort. The initial reports of these working groups, if they are completed by August 23, will be attached to final report of the workshop. However, the activities of these working groups are also relevant apart from the workshop, and so should not be prescribed by it. The workshop can be viewed as an impetus for further consensual infrastructure activities withing the temporal database community. The specific charters of the working groups will be determined by the coordinators. I now turn to discussing the particulars of the TSQL2 working group. The TSQL2 working group design will proceed in the context of the following constraints. * The initial design must be completed by August 23, 1993. * The design will be based on SQL2. In particular, none of the significant extensions envisioned in SQL3 will be assumed to be present. * Initially, the language design will support user-defined time and valid time. Support for transaction time may be added later. * The design will be implementable in the context of conventional relational database technology. In particular, implementations of the data model and query language constructs will be possible without necessitating major changes to conventional database management systems. * Discrete time will be assumed. * Past and future valid time will be supported. The activities of this working group will be parallel to those of the SQL2/3 and TSQL3 working groups. Interaction in the medium term between these groups will attempt to arrive at consistent approaches.