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XQuery, 2nd Edition by Priscilla Walmsley

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Chapter 25. 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 25-1.

Table 25-1. Optional features
FeatureDescriptionChapter/Section
ModuleSupport for library modules and module imports “Assembling Queries from Multiple Modules”
Schema AwareSupport for schema imports in the prolog and validate expressions Chapter 14
Typed DataSupport for typed element and attribute nodes Chapter 14
Static TypingDetection of all static type errors in the analysis phase Chapter 15
Higher-Order FunctionSupport for function items, inline function expressions, and dynamic function calls Chapter 23
SerializationAbility to serialize query results “Serializing Output”

In addition to these seven 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 ...

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