Carl-Alexander Wichert

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The rule-based update language ULTRA has been designed for the specification of complex database updates in a modular fashion. The logical semantics of update goals is based on update request sets, which correspond to deferred basic updates in the database. The declarative character of the logical semantics leaves much freedom for various evaluation(More)
The concept of logic databases can serve as a clear and expressive foundation of various kinds of information systems. However, classical logic languages refer to a single database state, whereas in modern information systems it is necessary to take dynamic behaviour into account. For this purpose, several update languages have been pro-which allow to(More)
In this paper a logical framework called ULTRA is presented that can serve as the basis for a variety of update languages, among others extensions of the database language SQL, accommodating nested update queries and universal quantification over updates. We give a complete definition of the syntax and semantics of the ULTRA language based on concepts of(More)
Electronic commerce plays a more and more important role in today's economy. An increasing number of firms sell their products online, and portals bundle the services of other firms and offer them to the user thereby acting as one single point of contact. An important aspect in this trend is the composition of various services to form value-added offerings.(More)