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Department of Informatics

Details Colloquium Spring 2015

05.03.2015 - Getting Down to Earth with SkyServer -- Identifying Interests of Many Users of a Databas

Speaker: Prof. Dr. Klemens Böhm
Host: Prof. Dr. Michael Böhlen


Many scientific databases nowadays are publicly available for querying and advanced data analytics. One prominent example is the Sloan Digital Sky Survey (SDSS) SkyServer, which offers data to astronomers, scientists, and the general public. With a large user base, it is worthwhile to identify the areas of the data space that are of interest to many users. This is beneficial for understanding the public focus, and the trending research directions on the subject described by the database, i.e., astronomy in the case of SkyServer. In a current research project, we study the problem of extracting and analyzing access areas of user queries, by analyzing the query logs of the database. To our knowledge, both the concept of access areas and how to extract them have not been studied before. We address these shortcomings by first proposing a novel notion of access area which is independent of any specific database state. It should allow to detect interesting areas of the data space, regardless if they have already existed in the database content. Second, we present a detailed mapping of our notion to different query types. Using our mapping on the SkyServer query log, we obtain a transformed data set. Third, we propose a new distance function to analyze this data set. Applying DBScan with our distance function, we arrive at access areas that are interesting from the perspective of an astronomer. These areas occupy only a small fraction (in some cases less than 1%) of the data space and are accessed by many users. Some frequently accessed areas even do not exist in the space spanned by available


Klemens Böhm is full professor (chair of databases and information systems) at Karlsruhe Institute of Technology (KIT), Germany, since 2004. Prior to that, he has been professor of applied informatics/data and knowledge engineering at University of Magdeburg, Germany, senior research assistant at ETH Zürich, Switzerland, and research assistant at GMD -- Forschungszentrum Informationstechnik GmbH, Darmstadt, Germany. Current research topics at his chair are knowledge discovery and data mining, data privacy and workflow management. Klemens gives much attention to collaborations with other scientific disciplines and with industry.

26.03.2015 - Efficiency and Equity Consequences of Transplant Organ Allocation Policies

Speaker: Prof. Utku Ünver, Ph.D.
Host: Prof. Sven Seuken, Ph.D.


Within the last decade kidney exchange has become a mainstream paradigm to increase the number of kidney transplants. However, compatible pairs do not participate, and the full benefit from exchange can be realized only if they participate. In this paper, we propose a new incentive scheme that relies on incentivizing participation of compatible pairs in exchange via insurance for the patient for a future renal failure. Efficiency and equity analyses of this scheme are conducted and compared with efficiency and equity outcomes of live donation and living donor organ exchange. We also present the potential role of such an incentive scheme to strengthen the national kidney exchange system.


Prof. Utku Ünver, Ph.D., a Professor of Economics at Boston College, is an economic theorist with research interests in market design, mechanism design, and game theory with emphasis on the theory and practice of matching markets and allocation/exchange of discrete resources. His recent research focuses on (a) the design and analysis of new organ allocation policies, including but not limited to kidney exchange clearinghouses; (b) axiomatic properties of matching and discrete resource allocation mechanisms, and probabilistic mechanisms; (c) improving recommendation systems used in adoption of children in foster care; (d) balanced exchange and matching in two-sided matching markets such as tuition exchange in college admissions, student exchange among colleges; (e) dynamic matching mechanisms and models; and (f) school choice mechanisms. He has also worked on implementing kidney exchanges and improving adoption schemes in real life with policy workers. He received his Ph.D. from University of Pittsburgh in 2000 in economics. He is the President of the Society for Economic Design and a Fellow of the Science Academy in Turkey.

23.04.2015 - Improving QoE for HTTP Adaptive Video Streaming

Speaker: Prof. Dr. Tobias Hoßfeld
Host: Prof. Dr. Burkhard Stiller


Video streaming services in the Internet are challenged by changing network conditions. Numerous video service providers are therefore employing HTTP adaptive streaming (HAS) as video delivery technology which adapts the video to the current network conditions. This requires monitoring of QoS parameters (like throughput and video buffer status) which allows to decide the quality level of the next video segment. The video contents are downloaded in segments, being available in multiple quality levels. The goal is to maximize QoE, i.e. minimizing video interruptions (due to video buffer underrun) whilst optimizing video quality. In this talk, the basic principles of HTTP adaptive streaming are explained. Key influence factors on QoE for HAS are identified and their effect size are assessed which builds the basis for a simple QoE model. QoE monitoring mechanisms can be derived which capture the relevant influence factors. The quality adaptation algorithms rely on this information and are the key to QoE for HAS. In order to benchmark such quality adaptation mechanisms, a QoE optimal adaptation strategy is proposed and formulated as a mixed integer linear program. Going beyond such in-session QoE management, the question arises whether additional context information about the current system state, e.g. from simultaneous out-of-band channels such as social network trend analytics, may help to further optimize QoE. Finally, an outlook on other promising research directions is given.


Prof. Dr. Tobias Hoßfeld is professor and head of the Chair "Modeling of Adaptive Systems" at the University of Duisburg-Essen, Germany, since 2014. He finished his Ph.D. in 2009 and his professorial thesis (habilitation) "Modeling and Analysis of Internet Applications and Services" in 2013 at the University of Würzburg, Chair of Communication Networks, where he was also heading the "Future Internet Applications & Overlays" research group. He has published more than 100 research papers in major conferences and journals, receiving 5 best conference paper awards, 3 awards for his Ph.D. thesis, and the Fred W. Ellersick Prize 2013 (IEEE Communications Society) for one of his articles on QoE. He is member of the advisory board of the ITC conference and if the editorial board of the IEEE Communications Surveys & Tutorials. He is currently involved in several projects: DFG Oekonet "Design and Performance Evaluation of New Mechanisms for the Future Internet – New Paradigms and Economic Aspects"; DFG QoE-DZ "Analysis and Optimization of the Trade-off between QoE and Energy-Efficiency in Data Centers"; DFG Crowdsourcing "Design and Evaluation of new mechanisms for crowdsourcing as emerging paradigm for the organization of work in the Internet"; COST ACROSS "Autonomous Control for a Reliable Internet of Services".

30.04.2015 - Software Design Sketchingonnecting Toys with Visible Light Communication

Speaker: Prof. André van der Hoek, Ph.D.
Host: Prof. Dr. Martin Glinz


Software design sketching refers to the near-ubiquitous practice of software designers to, when faced with a design problem, not immediately turn to advanced modeling tools, instead choosing to use pen-and-paper or the whiteboard to work through the problem and come up with a solution. A hallmark of this activity is that what the software designers draw and work with are sketches: rough, imprecise approximations of the design they have in mind that are continuously modified and refined as part of the design activity. Not much is understood about the sketches that software designers produce, the role they play, and how to help the designers in the process of creating and using them. What kinds of sketches do the designers create? How do they navigate among them? What do they use the sketches for? In this talk, I take a step back, place software engineering in a design perspective, illustrate the role of sketching, detail important sketch behaviors of professionals, and present a tool, Calico, designed to assist them in software design sketching.


André van der Hoek serves as chair of the Department of Informatics at the University of California, Irvine. He holds a joint B.S. and M.S. degree in Business-Oriented Computer Science from Erasmus University Rotterdam, the Netherlands, and a Ph.D. degree in Computer Science from the University of Colorado at Boulder. He heads the Software Design and Collaboration Laboratory, which focuses on understanding and advancing the roles of design, collaboration, and education in software development. He has authored and co-authored over 100 peer-reviewed journal and conference publications, and in 2006 was a recipient of an ACM SIGSOFT Distinguished Paper Award. He is a co-author of the 2005 Configuration Management Impact Report as well as the 2007 Futures of Software Engineering Report on Software Design and Architecture. He has served on numerous international program committees, was a member of the editorial board of ACM Transactions on Software Engineering and Methodology from 2008 to 2014, was program chair of the 2010 ACM SIGSOFT International Symposium on the Foundations of Software Engineering, and was program co-chair of the 2014 International Conference on Software Engineering. He was recognized as an ACM Distinguished Scientist in 2013, and in 2009 he was a recipient of the Premier Award for Excellence in Engineering Education Courseware. He is the principal designer of the B.S. in Informatics at UC Irvine and was honored, in 2005, as UC Irvine Professor of the Year for his outstanding and innovative educational contributions.

21.05.2015 - Crowd Agents: Creating Intelligent Interactive Systems from the Top Down

Speaker: Prof. Jeffrey Bigham, Ph.D.
Host: Prof. Dr. Abraham Bernstein


Over the past few years, I have been developing and deploying interactive crowd-powered systems that solve characteristic hard problems to help people get things done in their everyday lives. For instance, VizWiz answers visual questions for blind people in seconds, Legion drives robots in response to natural language commands, Chorus holds helpful general conversations with human partners, and Scribe converts streaming speech to text in less than five seconds.My research envisions a future in which the intelligent systems that we have dreamed about for decades, which have inspired generations of computer scientists from its beginning, are brought about for the benefit of people. My work illustrates a path for achieving this vision by leveraging the on-demand labor of people to fill in for components that we cannot currently automate, by building frameworks that allow groups to do together what even expert individuals cannot do alone, and by gradually allowing machines to take over in a data-driven way. A crowd-powered world may seem counter to the goals of computer science, but I believe that it is precisely by creating and deploying the systems of our dreams that will learn how to advance computer science to create the machines that will someday realize them.


Prof. Jeffrey P. Bigham, Ph.d., is an Associate Professor in the Human-Computer Interaction and Language Technologies Institutes in the School of Computer Science at Carnegie Mellon University. He uses clever combinations of crowds and computation to build truly intelligent systems, often with a focus on systems supporting people with disabilities. Dr. Bigham received his B.S.E degree in Computer Science from Princeton University in 2003, and received his Ph.D. in Computer Science and Engineering from the University of Washington in 2009. From 2009 to 2013, he was an Assistant Professor at the University of Rochester, where he founded the ROC HCI human-computer interaction research group. He has been a Visiting Researcher at MIT CSAIL, Microsoft Research, and Google[x]. He has received a number of awards for his work, including the MIT Technology Review Top 35 Innovators Under 35 Award, the Alfred P. Sloan Fellowship, and the National Science Foundation CAREER Award.

28.05.2015 - When Things Fall Apart: The Critical Role of Information Infrastructures When Responding to a Major Disaster

Speaker: Prof. Hans J. Scholl, Ph.D.
Host: Prof. Dr. Gerhard Schwabe


Around the world the frequency, scale, and impacts of natural and man-made disasters have markedly increased over the past decades. When a catastrophe strikes, local responders and communities are regularly vastly overwhelmed by the impact. Understanding the scale and scope of the impact, gaining situational awareness, and forming a common operating picture is the foremost task of any response. However, accurate and reliable information is the scarcest resource in such situations, so that it can take days and weeks until the extent of the impact is completely understood. Information and communication technologies (ICTs) play increasingly important roles in all phases of disaster and catastrophe management. Particularly, advanced ICTs have enabled government agencies and non-profit organizations to mobilize agile and flexible disaster response and recovery operations in the always dynamically changing situations of a disaster response. However, advanced ICTs have also introduced new vulnerabilities. The talk looks at select recent cases and discusses the complexities of response efforts, the range and capabilities of technologies in support of response management and summarizes the lessons learned. The talk finally raises and discusses the question to which extent disasters and catastrophes are truly natural, and which ones might be rather man-made.


Prof. Hans J (Jochen) Scholl, Ph.D. (Information Science, SUNY Albany) is an Associate Professor in the Information School at the University of Washington (2003 to present). His research expertise is focused on information management. Special topics of interest include electronic and smart government, process analysis, design, and engineering, interoperability, information artifact evaluation, complex systems, systems dynamics, as well as emergency, disaster, and catastrophe information management using novel information technologies as a major focus. He serves as an Associate Editor to Government Information Quarterly, the leading journal in electronic government. He chairs or co-chairs e-government conferences, such as the International Federation for Information Processing (IFIP) E-Government Conference, as well as the globally leading E-government Track and E-Government Symposium at the Hawaii International Conference on System Sciences (HICSS). Prof. Scholl is the Chair (2013 to 2017) of the IFIP TC3 WG 8.5 (Information Systems and Public Administration) and a past president of the Digital Government Society (2010-2011).

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