Introduction

This panel will discuss two issues. The first question is "To what extent should DBMS users be permitted/encouraged to participate in the process of determining an optimal query processing strategy?" In current DBMSs, at least two forms of user intervention have been observed: (a) In some systems, rephrasing a query may cause it to run faster. Can we expect to see implementations of query languages which are truly non-procedural, i.e., for which all forms of semantically equivalent queries will produce identical execution strategies? (b) Some systems allow a user to give "hints" to the optimizer (e.g., suggesting a preferred join ordering). Is a "hint" facility a valuable adjuct to a DBMS? If so, what kinds of hints or optimizations should be made available to users?