XQuery: The XML Query Language

Chapter 9. Type Operators

Introduction

As described in Chapters 1 and 2, every XQuery expression has a static (compile-time) type, even if the value is “untyped” (the type xdt:untypedAtomic). During evaluation, these expressions result in values, and the values have dynamic types (consistent with the static types of the expressions that produced them).

All XQuery implementations perform dynamic type checking, and some perform static type checking. Consequently, there are times when you need to change the type of an expression or value.

This chapter focuses on the many functions and operators XQuery provides for working with types. These operators break down into roughly four categories:

• Operators that cast values of one atomic type into values of ...