Portal alumni
(2016)
Die Universität Potsdam hat in diesem Jahr groß gefeiert: Sie ist 25 Jahre alt geworden. Zahlreiche Veranstaltungen und Publikationen zum Jubeljahr beleuchten, wie sich die Universität seit ihrer Gründung am 15. Juli 1991 entwickelt hat. Auch die Redaktion von Portal Alumni will dieses Vierteljahrhundert in den Blick nehmen und zwar aus der Perspektive der Studierenden und Alumni. Wir haben uns gefragt: Wie hat sich das Studium an der Universität Potsdam in der Vergangenheit geändert? Was ist den Studierenden heute wichtig, was waren wichtige Themen vor zehn oder zwanzig Jahren? Welche Erinnerungen haben Alumni an ihre Hochschulzeit? In diesem Heft lassen wir Alumni zu Wort kommen, die zu unterschiedlichen Zeiten an der Universität studiert haben und die für uns einen Blick zurück werfen auf ihre Generation. Mit dabei ist etwa Stefan Uhlmann, der sein Studium kurz vor dem Wendeherbst aufgenommen hatte. Sein erstes Semester war noch geprägt von sozialer Sicherheit: Der Staat zahlte den monatlichen studentischen Unterhalt von 200 Mark, die Universität stellte den Wohnheimplatz. Selbst der Arbeitsplatz war nach den Gesetzen der Planwirtschaft sicher. Wenige Monate später war alles anders: Die Inhalte aller Studiengänge wurden auf den Prüfstand gestellt, alle Rahmenbedingungen neu gestaltet, die gesamte Gesellschaft und damit auch der Arbeitsmarkt waren im Umbruch. Zwischen der Generation von Stefan Uhlmann und der der jungen Bachelorabsolventin Friederike Bath liegen 25 Jahre Universitätsgeschichte. Eine Zeit, in der sich Lehre und Studium gewandelt haben. Der Einführung von einer Studienordnung nach bundesdeutschem Recht folgte in der Jahrtausendwende die Bologna-Reform, die nicht nur das Studieren verändert hat. Sie hat auch einen Wertewandel mit sich gebracht, den der Sozialisationswissenschaftler Wilfried Schubarth in dieser Ausgabe beschreibt.
Design and Implementation of service-oriented architectures imposes a huge number of research questions from the fields of software engineering, system analysis and modeling, adaptability, and application integration. Component orientation and web services are two approaches for design and realization of complex web-based system. Both approaches allow for dynamic application adaptation as well as integration of enterprise application. Commonly used technologies, such as J2EE and .NET, form de facto standards for the realization of complex distributed systems. Evolution of component systems has lead to web services and service-based architectures. This has been manifested in a multitude of industry standards and initiatives such as XML, WSDL UDDI, SOAP, etc. All these achievements lead to a new and promising paradigm in IT systems engineering which proposes to design complex software solutions as collaboration of contractually defined software services. Service-Oriented Systems Engineering represents a symbiosis of best practices in object-orientation, component-based development, distributed computing, and business process management. It provides integration of business and IT concerns. The annual Ph.D. Retreat of the Research School provides each member the opportunity to present his/her current state of their research and to give an outline of a prospective Ph.D. thesis. Due to the interdisciplinary structure of the Research Scholl, this technical report covers a wide range of research topics. These include but are not limited to: Self-Adaptive Service-Oriented Systems, Operating System Support for Service-Oriented Systems, Architecture and Modeling of Service-Oriented Systems, Adaptive Process Management, Services Composition and Workflow Planning, Security Engineering of Service-Based IT Systems, Quantitative Analysis and Optimization of Service-Oriented Systems, Service-Oriented Systems in 3D Computer Graphics sowie Service-Oriented Geoinformatics.
Cost models are an essential part of database systems, as they are the basis of query performance optimization. Based on predictions made by cost models, the fastest query execution plan can be chosen and executed or algorithms can be tuned and optimised. In-memory databases shifts the focus from disk to main memory accesses and CPU costs, compared to disk based systems where input and output costs dominate the overall costs and other processing costs are often neglected. However, modelling memory accesses is fundamentally different and common models do not apply anymore. This work presents a detailed parameter evaluation for the plan operators scan with equality selection, scan with range selection, positional lookup and insert in in-memory column stores. Based on this evaluation, a cost model based on cache misses for estimating the runtime of the considered plan operators using different data structures is developed. Considered are uncompressed columns, bit compressed and dictionary encoded columns with sorted and unsorted dictionaries. Furthermore, tree indices on the columns and dictionaries are discussed. Finally, partitioned columns consisting of one partition with a sorted and one with an unsorted dictionary are investigated. New values are inserted in the unsorted dictionary partition and moved periodically by a merge process to the sorted partition. An efficient attribute merge algorithm is described, supporting the update performance required to run enterprise applications on read-optimised databases. Further, a memory traffic based cost model for the merge process is provided.