05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
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Item Open Access A design space for pervasive advertising on public displays(2013) Alt, Florian; Schmidt, Albrecht (Prof. Dr.)Today, people living in cities see up to 5000 ads per day and many of them are presented on public displays. More and more of these public displays are networked and equipped with various types of sensors, making them part of a global infrastructure that is currently emerging. Such networked and interactive public displays provide the opportunity to create a benefit for society in the form of immersive experiences and relevant content. In this way, they can overcome the display blindness that evolved among passersby over the years. We see two main reasons that prevent this vision from coming true: first, public displays are stuck with traditional advertising as the driving business model, making it difficult for novel, interactive applications to enter the scene. Second, no common ground exists for researchers or advertisers that outline important challenges. The provider view and audience view need to be addressed to make open, interactive display networks, successful. The main contribution made by this thesis is presenting a design space for advertising on public displays that identifies important challenges -- mainly from a human-computer interaction perspective. Solutions to these core challenges are presented and evaluated, using empirical methods commonly applied in HCI. First, we look at challenges that arise from the shared use of display space. We conducted an observational study of traditional public notice areas that allowed us to identify different stakeholders, to understand their needs and motivations, to unveil current practices used to exercise control over the display, and to understand the interplay between space, stakeholders, and content. We present a set of design implications for open public display networks that we applied when implementing and evaluating a digital public notice area. Second, we tackle the challenge of making the user interact by taking a closer look at attracting attention, communicating interactivity, and enticing interaction. Attracting attention is crucial for any further action to happen. We present an approach that exploits gaze as a powerful input modality. By adapting content based on gaze, we are able to show a significant increase in attention and an effect on the user's attitude. In order to communicate interactivity, we show that the mirror representation of the user is a powerful interactivity cue. Finally, in order to entice interaction, we show that the user needs to be motivated to interact and to understand how interaction works. Findings from our experiments reveal direct touch and the mobile phone as suitable interaction technologies. In addition, these findings suggest that relevance of content, privacy, and security have a strong influence on user motivation. Third, this thesis makes a set of contributions towards understanding audience behavior, which is particularly important for advertisers in order to choose appropriate content and to select suitable locations for future advertising displays. Our findings provide an in-depth understanding of the honeypot effect as a powerful interactivity cue. Furthermore, we identify a number of interesting effects (e.g., the landing effect) and explain how developers could design for them. We envision the results of this thesis to provide a basis for future research and for practitioners to shape future advertisements on public displays in a positive way.Item Open Access Scalable computer network emulation using node virtualization and resource monitoring(2011) Maier, Steffen Dirk; Rothermel, Kurt (Prof. Dr. rer. nat. Dr. h. c.)Ongoing development of computer network technology requires new communication protocols on all layers of the protocol stack to adapt to and to exploit technology specifics. The performance of new protocol implementations has to be evaluated before deployment. Computer network emulation enables the execution of real unmodified protocol implementations within a configurable synthetic environment. Since network properties are reproduced synthetically, emulation supports reproducible measurement results for wired and wireless networks. Meaningful evaluation scenarios typically involve a large number of communicating nodes. Reproducing the network properties of the medium access control layer can be accomplished efficiently on cheap common off the shelf computers and allows to evaluate network protocols, transport protocols, and applications. However, meaningful emulation scenario sizes often require more nodes than affordable computers. To scale the number of nodes in an emulation scenario beyond the available computers, we discuss approaches to virtualization and operating system partitioning. Focusing on the latter, we argue for virtual protocol stacks, which provide an extremely lightweight node virtualization enabling the execution of multiple instances of software to be evaluated on each physical computer. To connect virtual nodes on the same and on different computers, we design and implement a highly efficient software communication switch. A centralized emulation control component distributes dynamic network property updates which result from node mobility for instance. To handle the large number of nodes and thus increased updates, we propose a hierarchical control where the central component delegates updates to sub-components distributed over the computers of an emulation system. Extensive evaluations show the scalability of our virtualized network emulation system. Virtual nodes executed on the same computer share its limited resources. Hosting too many virtual nodes on the same computer may lead to resource contention. This can cause unrealistic measurement results and is thus undesirable. Discussing different approaches to handle resource contention, we argue for detection and recovery. We define quality criteria that allow the detection of resource contention. In order to observe those quality criteria during emulation experiments, we propose a highly lightweight monitoring approach. Our monitoring is based on instrumenting an operating system kernel and observing basic resource scheduling events. This enables the detection of even peak resource usage within a split second. Thorough evaluations demonstrate the effectiveness of quality criteria and monitoring as well as the negligible overhead of our monitoring approach.Item Open Access Event knowledge and models of logical metonymy interpretation(2014) Zarcone, Alessandra; Padó, Sebastian (Prof. Dr.)During language understanding, people do not only rely on what they read or hear, but they also exploit implicit information. For example, when they process the expression "begin the book", they understand it involves an event which is not explicitly mentioned (e.g. "begin reading the book). This thesis looks at these constructions, known as logical metonymies, which combine an event-selecting verb and entity-denoting object and involve covert events. Logical metonymies are an interesting challenge for theories of lexical semantics: they need to be reconciled with compositionality, they require the integration of context (writers typically write books, students typically read them), and they lie at the interface between lexicon and world knowledge (is the information that books are read stored in our mental lexicon or in our world knowledge?). I critically analyze previous hypotheses on logical metonymy with regard to the answer they provide to two core problems: the source problem (what events are retrieved? what type of event knowledge is assumed?) and the trigger problem (why do some constructions trigger a metonymic interpretation and others do not?). Lexicalist approaches claim that the metonymy arises from a type clash between the event-selecting verb and an entity-denoting object, and posit complex lexical items, encoding event information about artifacts (e.g. book: read), to explain the recovery of covert events. Pragmatic-based approaches argue against the idea that lexical items have an internal structure, suggesting that covert events arise from the underspecification of a logical metonymy and are inferred via non-lexical knowledge. I look with particular attention at the role of event knowledge, which lexicalist approaches place in our mental lexicon, while pragmatic-based approaches place it in our world knowledge. I propose a third hypothesis, based on thematic fit and generalized event knowledge of typical events and their participants, which have been shown to guide efficient incremental processing: I argue that contextual elements cue generalized event knowledge, which plays a key role in determining the covert event for a logical metonymy. I explore this hypothesis from an interdisciplinary perspective, employing both psycholinguistic experiments and computational models, in order to seek converging evidence and confront it with the theoretical investigation. The results from the psycholinguistic experiments and from the computational (distributional) models support the hypothesis that covert event retrieval is guided by generalized event knowledge. I also employ the computational models to analyze previous experimental results and to explore the hypothesis that thematic fit, informed by generalized event knowledge, is ultimately responsible for the trigger of the logical metonymy. I then report on more psycholinguistic evidence showing that a notion of type is indeed necessary to account for differences between metonymic and non-metonymic constructions, and that both type and thematic fit play a role in logical metonymy interpretation. Lastly, I argue for a context-sensitive model of logical metonymy interpretation that exploits an information-rich lexicon, but needs to rethink the notion of type and reconcile it with the notion of thematic fit.Item Open Access Cognition-aware systems to support information intake and learning(2016) Dingler, Tilman; Schmidt, Albrecht (Prof. Dr.)Knowledge is created at an ever-increasing pace putting us under constant pressure to consume and acquire new information. Information gain and learning, however, require time and mental resources. While the proliferation of ubiquitous computing devices, such as smartphones, enables us to consume information anytime and anywhere, technologies are often disruptive rather than sensitive to the current user context. While people exhibit different levels of concentration and cognitive capacity throughout the day, applications rarely take these performance variations into account and often overburden their users with information or fail to stimulate. This work investigates how technology can be used to help people effectively deal with information intake and learning tasks through cognitive context-awareness. By harvesting sensor and usage data from mobile devices, we obtain people's levels of attentiveness, receptiveness, and cognitive performance. We subsequently use this cognition-awareness in applications to help users process information more effectively. Through a series of lab studies, online surveys, and field experiments we follow six research questions to investigate how to build cognition-aware systems. Awareness of user's variations in levels of attention, receptiveness, and cognitive performance allows systems to trigger appropriate content suggestions, manage user interruptions, and adapt User Interfaces in real-time to match tasks to the user's cognitive capacities. The tools, insights, and concepts described in this book allow researchers and application designers to build systems with an awareness of momentary user states and general circadian rhythms of alertness and cognitive performance.Item Open Access Effiziente Gestaltung und Anwendung von attributbasierter Zugriffskontrolle für RESTful Services(2019) Hüffmeyer, Marc; Mitschang, Bernhard (Prof. Dr.)Item Open Access Digital pre- and post-equalizers for in-car data transmission over plastic optical fibers(2014) Voigt, Yixuan; Speidel, Joachim (Prof. Dr.-Ing. )Lately, a hot topic in the automobile industry is the development of the in-vehicle infotainment communication network based on the media oriented system transport (MOST) standard, where a cost-effective optical physical layer composed of light emitting diodes (LED), plastic optical fibers (POF) and positive-intrinsic-negative photodiodes (PIN PD) is used by the in-car network. The latest MOST150 standard has specified a transmission speed of 150 Mbit/s, while the next MOST generation is targeted at multi-Gbit/s. Obviously, the very limited bandwidth of the current physical layer will weigh on the future MOST generations. However, it is important to evaluate the potential of the current physical layer, for the reason that the car-manufacturers may continue using the low-cost and easily operable POFs and LEDs. The objective of this dissertation is to increase the data-rate for the next MOST generation from 150 Mbit/s to 2 ∼ 3 Gbit/s, based upon the current MOST150 optical physical layer. The main emphasis lies in investigating electronic signal processing techniques to detect the multi-level pulse-amplitude modulated (MPAM) signal transmitted through the noisy dispersive POF-based optical channel. To be specific, four different transmission schemes are studied respectively: the post-equalization scheme using either linear or decision-feedback equalizer, the joint pre- and post-equalization scheme, the non-linear Tomlinson-Harashima precoding (THP) scheme, and the bidirectional decision feedback equalization (BiDFE) scheme. In the BiDFE scheme, a novel trellis-based BiDFE (TB-BiDFE) equalizer is proposed. Their performances are investigated by means of theoretical analysis and computer simulations. As will be shown, with the help of electronic equalizers and error-correcting code, the final bitrate is able to reach 3 Gbit/s over a 10 m standard step-index POF, despite the use of a low-cost LED transmitter.Item Open Access Efficient programmable deterministic self-test(2010) Hakmi, Abdul-Wahid; Wunderlich, Hans-Joachim (Prof. Dr. habil.)In modern times, integrated circuits (ICs) are used in almost all electronic equipment ranging from household appliances to space shuttles and have revolutionized the world of electronics. Continuous reductions in the manufacturing costs as well as the size of this technology have allowed the development of very sophisticated ICs for common use. Post fabrication testing is necessary for each IC in order to ensure the quality and the safety of human life. The improvement in technology as well as economies of scale are continuously reducing fabrication costs. On the other hand, the increasing complexity of circuits is leading to higher test costs. These increasing test costs affect the market price of a chip. A test set is a set of binary patterns that are applied on the circuit inputs to detect the potential faults. Only a small number of bits in a test set are specified to 0 or 1 called care bits while other bits called don't care bits may assume random values. Test sets volume is characterized by the number of patterns as well as the size of each pattern in a test set. The increasing number of gates in nanometer ICs has resulted in an explosive increase in test sets volume. This increase in test sets volume is the major cause for rapidly growing test costs. An IC is tested either by using an automatic test equipment (ATE) or with the help of special hardware added on-chip that performs a self-test. These two approaches as well as their hybrid derivatives offer various trade-offs in test costs, quality, reliability and test time. In ATE testing high test sets volume leads to the requirement of expensive testers with large storage capacity while in self-test it results in significant hardware overhead. A test set is highly compressible due to the presence of a large number of don't care bits. The Test data compression techniques are used to limit test sets volume and hence the involved test cost. These compressed test sets are applicable to both ATE and Self-test methodologies. Compression of a test set depends on its statistical attributes such as the percentage and the distribution of care bits. The available test compression schemes assume that all the test sets have similar statistical attributes which is not always true. These attributes vary considerably among various test sets depending on the circuit structure and the targeted trade-offs. To get optimized reduction in test sets volume, test sets with different statistical attributes have to be addressed separately. In this work we analyze various test sets of industrial circuits and categorize them into three classes based on their statistical attributes. By examining each class differently, three novel compression methods and decompression architectures are proposed. The proposed test compression methods are equally adaptable in ATE testing and self-test. Three low cost programmable self-test schemes offering various trade-offs in testing are developed by applying these methods. The experimental results obtained with the test sets of large industrial circuits show that the proposed compression methods reduce storage requirements by more than half compared to the most efficient available methods. First time in literature the total number of bits in a compressed test set are lesser than the number of care bits in the original test set. The additional advantages of proposed methods include guaranteed encoding, significant reduction in decompression time overhead and programmability of decompression hardware.Item Open Access Optimierung datenintensiver Workflows: Konzepte und Realisierung eines heuristischen, regelbasierten Optimierers(2011) Vrhovnik, Marko; Mitschang, Bernhard (Prof. Dr.-Ing. habil.)Um die Modellierung datenintensiver Workflows, die große relationale Datenmengen verarbeiten, zu vereinfachen, wurden Workflowbeschreibungssprachen, wie BPEL, von führenden Herstellern von Workflow- und Datenbankmanagementsystemen um SQL-Funktionalität erweitert. Dadurch müssen Datenverarbeitungsoperationen, wie SQL-Anweisungen oder Aufrufe benutzerdefinierter Prozeduren, nicht mehr in Web-Services gekapselt werden, sondern können direkt auf der Workflowebene definiert werden. Daraus resultiert eine neue Möglichkeit der Anfrageoptimierung, die existierende Optimierungsansätze in Datenbanksystemen ergänzt: Suboptimal modellierte Datenverarbeitungsoperationen lassen sich in einer Workflowbeschreibung unter Verwendung von Restrukturierungsregeln derart transformieren, dass sie von einem Workflow- bzw. Datenbankmanagementsystem wesentlich effizienter ausgeführt werden können. In dieser Doktorarbeit werden Konzepte zur Realisierung eines heuristischen, regelbasierten Optimierers für datenintensive Workflows vorgestellt. Der Optimierer wendet eine Regelbasis gemäß einer wohldefinierten Kontrollstrategie auf eine interne Repräsentation für datenintensive Workflows, dem sogenannten Prozessgraphenmodell (PGM), an, um die Datenverarbeitung eines datenintensiven Workflows zu optimieren. PGM erlaubt eine effiziente und sprachunabhängige Definition und Anwendung der Restrukturierungsregeln und unterstützt somit eine Optimierung von Datenverarbeitungsoperationen, die in unterschiedlichen Beschreibungssprachen definiert sein können. Die Regelbasis enthält Restrukturierungsregeln, die auf existierenden und neuen Optimierungsstrategien beruhen. Insbesondere nutzen die Restrukturierungsregeln das Wissen über Abhängigkeiten in einer Workflowbeschreibung aus, um die darin eingebetteten Datenverarbeitungsoperationen unter Beibehaltung der ursprünglichen Ausführungssemantik eines datenintensiven Workflows zu optimieren. Die Kontrollstrategie bestimmt, welche Restrukturierungsregeln in welcher Reihenfolge auf welche Teile einer Workflowbeschreibung angewendet werden, um zum einen das Optimierungspotential eines datenintensiven Workflows umfassend zu nutzen und zum anderen die Korrektheit der Regelanwendungen sicherzustellen. Die ausführliche Beschreibung des Prozessgraphenmodells, der Regelbasis und der Kontrollstrategie stehen im Mittelpunkt dieser wissenschaftlichen Abhandlung. Des Weiteren wird eine prototypische Implementierung des Optimierungsansatzes vorgestellt, welche dessen praktische Einsatzfähigkeit unterstreicht. Schließlich wird die Effektivität der einzelnen Restrukturierungsregeln mithilfe verschiedener Messszenarien untersucht. Dabei wird gezeigt, dass durch Anwendung der Restrukturierungsregeln Leistungssteigerungen in mehreren Größenordnungen erreicht werden können.Item Open Access Casual analytics : advancing interactive visualization by domain knowledge(2014) Bosch, Harald; Ertl, Thomas (Prof. Dr.)The often cited information explosion is not limited to volatile network traffic and massive multimedia capture data. Structured and high quality data from diverse fields of study become easily and freely available, too. This is due to crowd sourced data collections, better sharing infrastructure, or more generally speaking user generated content of the Web 2.0 and the popular transparency and open data movements. At the same time as data generation is shifting to everyday casual users, data analysis is often still reserved to large companies specialized in content analysis and distribution such as today's internet giants Amazon, Google, and Facebook. Here, fully automatic algorithms analyze metadata and content to infer interests and believes of their users and present only matching navigation suggestions and advertisements. Besides the problem of creating a filter bubble, in which users never see conflicting information due to the reinforcement nature of history based navigation suggestions, the use of fully automatic approaches has inherent problems, e.g. being unable to find the unexpected and adopt to changes, which lead to the introduction of the Visual Analytics (VA) agenda. If users intend to perform their own analysis on the available data, they are often faced with either generic toolkits that cover a broad range of applicable domains and features or specialized VA systems that focus on one domain. Both are not suited to support casual users in their analysis as they don't match the users' goals and capabilities. The former tend to be complex and targeted to analysis professionals due to the large range of supported features and programmable visualization techniques. The latter trade general flexibility for improved ease of use and optimized interaction for a specific domain requirement. This work describes two approaches building on interactive visualization to reduce this gap between generic toolkits and domain-specific systems. The first one builds upon the idea that most data relevant for casual users are collections of entities with attributes. This least common denominator is commonly employed in faceted browsing scenarios and filter/flow environments. Thinking in sets of entities is natural and allows for a very direct visual interaction with the analysis subject and it stands for a common ground for adding analysis functionality to domain-specific visualization software. Encapsulating the interaction with sets of entities into a filter/flow graph component can be used to record analysis steps and intermediate results into an explicit structure to support collaboration, reporting, and reuse of filters and result sets. This generic analysis functionality is provided as a plugin-in component and was integrated into several domain-specific data visualization and analysis prototypes. This way, the plug-in benefits from the implicit domain knowledge of the host system (e.g. selection semantics and domain-specific visualization) while being used to structure and record the user's analysis process. The second approach directly exploits encoded domain knowledge in order to help casual users interacting with very specific domain data. By observing the interrelations in the ontology, the user interface can automatically be adjusted to indicate problems with invalid user input and transform the system's output to explain its relation to the user. Here, the domain related visualizations are personalized and orchestrated for each user based on user profiles and ontology information. In conclusion, this thesis introduces novel approaches at the boundary of generic analysis tools and their domain-specific context to extend the usage of visual analytics to casual users by exploiting domain knowledge for supporting analysis tasks, input validation, and personalized information visualization.Item Open Access Ultra-high-speed digital-to-analog converter for optical communications(2019) Huang, Hao; Berroth, Manfred (Prof. Dr.-Ing.)In der vorliegenden Dissertation wird die Schaltungstechnik für schnelle DACs untersucht und ein DAC mit einer Umsetzungsrate bis zu 100 GS/s und 8 bit nomineller Auflösung in 28 nm CMOS Technologie entworfen. Um die Ausgangsbandbreite zu erhöhen, ist die Ausgangsstufe mit einer verteilten Struktur konstruiert. Dabei sind das Stromsummationsnetzwerk und die Taktverteilung an der DAC-Ausgangsstufe mittels künstlich konstruierten Leitungen realisiert, um die parasitären Kapazitäten auf die künstliche Leitung zu verteilen. Für die Charakterisierung des DACs ist ein 1 kByte Speicher integrierte, der zyklisch ausgelesen werden kann, um die Eingangsdatenströme für den DAC zu erzeugen. Die maximale Bandbreite beträgt 13 GHz bei einer Abtastrate von 100 GS/s. Die effektive Anzahl von Bits (engl. effective number of bits, ENOB) beträgt 5,3 bit bei niedrigen Ausgangsfrequenzen und reduziert sich auf 3,2 bit bei 24,9 GHz mit einer Abtastraten von 100 GS/s.