Digitales Video

Elektronische Dokumente werden immer häufiger durch zeitbasierte Medienobjekte wie z.B. Videoclips angereichert. Selbst im WWW sind mittlerweile Videos komfortabel durch Streamingtechnologie verfügbar. Rechnergestützte Videoschnittlösungen und Telekonferenzsysteme sind zudem weitere Einsatzfelder für digitale Videosequenzen. Aufgrund beschränkter Ressourcen ist Kompression aber weiterhin ein entscheidender Einsatzfaktor

On the completeness of object-creating database transformation languages

Object-oriented applications of database systems require database transformations involving non-standard functionalities such as set manipulation and object creation, i.e., the introduction of new domain elements. To deal with these functionalities, Abiteboul and Kanellakis introduced the \determinate" transformations as a generalization of the standard domain-preserving transformations. The obvious extensions of complete standard database programming languages, however, are not complete for the determinate transformations. To remedy this mismatch, the \constructive " transformations are proposed. It is shown that the constructive transformations are precisely the transformations that can be expressed in said extensions of complete standard languages. Thereto, a close correspondence between object creation and the construction of hereditarily nite sets is established. A restricted version of the main completeness result for the case where The present paper is concerned with the expressive power of object-creatin