Choosing a View Update Translator by Dialog at View Definition Time

We consider the problem of updating databases through views composed of selections, projections, and joins of a series of Boyce-Codd Normal Form relations. This involves translating updates expressed against the view to updates expressed against the database. Previously, we enumerated all translations of view updates into database updates that satisfy five criteria. This enumeration shows that the problem of translating view updates to database updates is inherently ambiguous. We give examples of structurally similar views that should have different translations because of the real world semantics. We propose that these semantics be obtained at view definition time. We show how this can be done through a structured dialog with the database administrator to choose a view update translator at view definition time. The questions asked during this dialog are based on the view definition, database structural schema information, and the answers to earlier questions in the dialog. Based on these questions a specific translator is chosen. Using this translator, userspecified view updates can be translated into database This work was started while the author was at the Computer Science Department of Stanford University. This work was sup ported in part by contract NSQ-84-C-0211 (the Knowledge Base Management Systems Project, Prof. Gio Wiederhold, PI) from the Defense Advanced Research Projects Agency and by contract AFOSR-80-0212 (Universal Relations, Prof. Jeff Ullman, PI) from the Air Force OWce of Scientillc Research, both of the United States Department of Defense, and by the Computer Sciences Research and Development Fund of The University of Texas at Austin. The views and conclusions contained in this document are those of the authors and should not be interpreted as representative of the oflicial policies of DARPA, the US Government, or the State of Texas. Author’s address: The University of Texas at Austin, Department of Computer Sciences, Austin, TX 78712-1188. updates without the need for any disambiguating dialog. However, dialog with the user may be desired to con6rm that the (view) side effects resulting from the user’s view update request are acceptable.