ONVIF has introduced the add-on concept to enable greater flexibility and speed in marketing feature interoperability. An add-on enables an ONVIF profile conformant device or client to conform to additional, and thus optional, capabilities outside of profiles. Because add-on features are limited in scope compared with profile feature sets, the development and release of add-on specifications and test tools can potentially be easier and quicker than with a profile.
An ONVIF add-on consists of at least one or more features that solve one use case. An add-on, by itself, is not comprehensive enough to qualify as a profile. Features of an add-on cannot already be covered in an existing, non-deprecated profile. Specifications for add-ons cannot include optional requirements for devices/clients or conditional requirements for devices. Add-ons are adaptable to changing technology/specification requirements due to version handling. New features can be added, and existing ones removed from an add-on if there is sufficient market motivation.
Devices and clients that want to claim conformance to add-ons must pass add-on conformance tests, as well as conform to an ONVIF profile. Once add-ons are available, they will be listed on the ONVIF Conformant Products web page. No add-on is available to date.
Go here to read how add-ons differ from profiles. And click here for more details about the creation, modification and deprecation process, and rules to ONVIF add-ons, as well as ONVIF profiles.