The Defined Context Set (DCS) is a context described in the International Telecommunication Union
(ITU) Recommendation X.216 for the delivery and use of presentation layer services. The Presentation Layer is responsible for matching the various Transfer Syntaxes with the Abstract Syntaxes by the application instances when they exchange their information at the Presentation Layer. The application instances must assume that the presentation layer supports the Transfer Syntax. The responding application instance relies on appropriate presentation contexts, referred to as a Defined Context Set (DCS).