XQuery

Chapter 23. Implementation-Specific Features

XQuery can be used for a wide variety of XML processing needs. As such, different XQuery implementations provide customized functions and settings for specific use cases. This chapter looks at some of the implementation-specific aspects of XQuery.

Conformance

The XQuery specification consists of a core set of features that all implementations are required to support. Supporting these features is known as minimal conformance. In addition, there are a handful of optional features that are clearly defined and scoped. These optional features are listed in Table 23-1.

Table 23-1. Features

Feature	Description	Chapter
Full Axis	Support for the axes ancestor, ancestor-or-self, following, following-sibling, preceding, preceding-sibling	4
Module	Support for library modules and module imports	12
Schema Import	Support for schema imports in the prolog	13
Schema Validation	Support for validate expressions	13
Static Typing	Detection of all static type errors in the analysis phase	14
Serialization	Ability to serialize query results to an XML document	22

In addition to these six features, some aspects of the core language are either implementation-dependent or implementation-defined. Implementation-defined features are those where the implementer is required to document the choices she has made. For example, the list of supported collations or additional built-in functions is implementation-defined. Implementation- ...