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)
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)
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 proposed, among them(More)
In a prospective study 113 extremities of 98 patients with suspected lower extremity deep venous thrombosis were examined by duplex sonography and phlebography. In 66 examinations phlebography demonstrated fresh thromboses which were limited to the calf in 14 cases. In all other cases thrombosis was partially or totally localized above the knee. Duplex(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)
Lung or lobe torsion may occur after thoracic surgery, chest trauma, pneumothorax, pneumonia or even spontaneously. Lung infarction is a possible complication. The characteristic radiological signs on plain radiographs are opacification and/or displacement of lobes and hilus structures. CT-signs of haemorrhagic infarction are opacification and multiple(More)