The namespace http://jsoniq.org/functions is used for JSONiq builtin functions defined by this specification. This namespace is exposed to the user and is bound by default to the prefix jn. For instance, the function name jn:keys() is in this namespace.

The namespace http://jsoniq.org/types is used for JSONiq builtin types defined by this specification (including synonyms for some XQuery types). This namespace is exposed to the user and is bound by default to the prefix js. For instance, the type name js:null is in this namespace.

The namespace http://jsoniq.org/default-function-namespace is a proxy namespace that maps to the jn: (JSONiq), fn: (XQuery) and math: (XQuery) namespaces. It is the default function namespace, allowing to call all these functions with no prefix.

The namespace http://jsoniq.org/default-type-namespace is a proxy namespace that maps to the js: (JSONiq) and xs: (XQuery) namespaces. It is the default type namespace, allowing to use all builtin types with no prefix.

Accessors used in JSONiq Data Model use the jdm: prefix. These functions are not exposed to the user and are for explanatory purposes of the data model within this document only. The jdm: prefix is not associated with a namespace.