Recommendation ITU-T H.761 gives the specification of the nested context language (NCL) and of an NCL presentation environment called Ginga-NCL to provide interoperability and harmonization among Internet protocol television (IPTV) multimedia application frameworks.NCL is a declarative glue language that holds media object presentations synchronized in time and space,no matter the types of the media objects.Ginga-NCL is an NCL presentation engine built as a component of a digital television (DTV) middleware.This Recommendation includes an electronic attachment containing NCL 3.1 module schemas used in the enhanced DTV profile.