This paper describes an object-oriented application framework RADIUS, which facilitates automatic Application Delivery, Installation and Upgrade (ADIU). By extending the object-oriented programming paradigm to the document and file level, application files can be located and delivered through a mechanism similar to dynamic dispatch in most OOP languages and systems. RADIUS is designed to be document-centric. All necessary information is stored with the documents and assigned at the application developers' end and thus requires no user intervention of any kind in locating, installing and upgrading applications. RADIUS is light-weight and requires no extensions to the programming languages and operating systems, and therefore is easy to integrate with other object or component systems.