Extension types are provided by the Framework or are defined and implemented by N4 application developers. An extension type specifies how and where a code extension may be used. Extension types can be provided as part of the N4 framework, or they may be implemented by third-party application developers. They are loaded into the memory at run time. When implementing code extensions, you must comply with the Java interface. Externally supported APIs have the com.Navis.external interface.