The design of XQuery has been a process of resolving the tensions between conflicting goals. It has been a slow process, and compromise has frequently been necessary.

The designers of XQuery did not begin with a blank slate. The Query data model was largely dictated by XML itself and by related W3C Recommendations such as XML Namespaces. The design of the language was also constrained by compatibility with existing standards such as XPath and XML Schema. Reconciling these constraints was not straightforward—for example, XPath Version 1 has only four types and a rather loose set of rules for type conversions, whereas XML Schema has forty-four built-in atomic types, a complex syntax for defining new types, and a strict set of rules for ...

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