Fraunhofer Institut für Integrierte Publikations-und Informationssysteme IPSI
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PublicationAdaptive outsourcing in cross-organizational workflows(GMD Forschungszentrum Informationstechnik, 1998)
;Klingemann, J. ;Wäsch, J.Aberer, K.Competitive markets force companies to minimize their costs while at the same time offering solutions which are tailored to the needs of their customers. This requires organizations to outsource at least parts of the overall effort and to rely on services which have to be provided by external partners, leading ultimately to virtual enterprises. The workflow concept has been very successful in coordinating and streamlining business processes but is so far limited to a single organization. Any attempt to distribute workflows among different organizations has to face the problems posed by the complex relationship among autonomous organizations and their services. To address these problems we propose a serviceoriented model for cross-organizational workflows. Modeling the workflow execution as a cooperation of services allows different organizations to interact via well-defined interfaces. We further show how the execution can be optimized by selecting services depending on their contribution to quality criteria of the workflow.
PublicationVIRGILIO - The metaphor definition tool(GMD Forschungszentrum Informationstechnik, 1998)
;L'Abbate, M.Hemmje, M.The Virgilio software system is a general purpose exploration tool for large collections of complex structured data. It generates visualisations of the results of a query to a database by the help of virtual reality objects, embedded into predefined virtual reality scenarios. This document describes the design, specification, and implementation of the Metaphor Definition Tool. This component of the Virgilio software system has to identify the most suitable virtual worlds for representing the result of a query. This is achieved by considering the metaphor definition task as a general constraint satisfaction problem. The logical formalism adopted to describe interrelationships among the involved objects corresponds to that of the Prolog programming language, in order to take advantage from its built in backtracking strategy. This paper presents the overall Virgilio architecture, provides a brief introduction to the concept of metaphor and its use within the Virgilio environment, contains a description of the MDT as well as a description of the repositories, and explains how to integrate the MDT into the whole system. Two complex mapping examples are also introduced.
PublicationAn admission control framework for applications with variable consumption rates in client-pull architectures(GMD Forschungszentrum Informationstechnik, 1998)
;Hollfelder, S.Aberer, K.Highly interactive multimedia applications require variable data rates during their presentation. Current admission control mechanisms do not address the variable data rate requirements appropriately for the following reasons: (1) classical admission control mechanisms are based on the server-push approach, where the required data rate has to be estimated in advance, and (2) worst-case resource reservation is not economic. Client-pull models are more appropriate to serve these kinds of applications. At the current state, there are no suitable mechanisms that support admission control in client-pull architectures at the server. In this paper, a session-oriented framework for admission control is introduced that is based on two steps: (1) the admission of new clients and (2) the scheduling of the single requests of admitted clients to balance the load. The goal of this approach is to improve the server utilization and the Quality of Service. Evaluation studies demonstrate the benefit of the framework.