GENERALIZED TUPLE SELECTION PREDICATES

Abstract

Tuple selection predicates (such as CITY = "Brighton*) provide the basis for both the Select and Join operators in the relational model (RM). Several proposed extensions to RM can be seen as relaxing the First Normal Form constraint of simple values to allow function-valued attributes. In order to take advantage of these complex values the class of allowable tuple selection predicates likewise needs to be extended. We propose a class of general tuple selection predicates based upon a general model allowing function values of any type constructed from some basic set of primitive domain types, and we investigate how various recent proposals fit into this general framework.