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.
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 |
4 |
Module |
Support for library modules and module imports |
12 |
Schema Import |
13 | |
Schema Validation |
Support for |
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-dependent behavior may vary by implementation but does not have to be explicitly stated in the documentation and cannot necessarily be predicted. For example, when an unordered
expression is used, the order of the results is implementation-dependent.
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