The purpose of the NAV-3b Metadata Extensions subview is to document any deviations of the architecture's subviews from the standard subview guidelines of the NAF, in terms of deviations from the NAF metamodel (NMM), which underpins all standard subviews of the NAF.

Even though the NAV-3b subview is used to stress the differences between the NMM definition and the HOPEX NAF implementation, the default behavior will be to integrate the metamodel diagrams describing the HOPEX implementation of the NMM.

The user can add his/her own set of metamodels and can also note the differences as a link comment in the report instance or by adding comments in the diagrams themselves.