Automated vehicles will eventually operate safely without the need of human supervision and fallback, nevertheless, scenarios will remain that are managed more efficiently by a human driver. A common approach to overcome such weaknesses is to shift control to the driver. Control transitions are challenging due to human factor issues like post-automation behavior changes. We thus investigated cooperative overtaking wherein driver and vehicle complement each other: drivers support the vehicle to perceive the traffic scene and decide when to execute a maneuver whereas the system steers. We explored two maneuver approval and cancel techniques on touchscreens, and show that cooperative overtaking is feasible, both interaction techniques provide good usability and were preferred over manual maneuver execution. However, participants disregarded rear traffic in more complex situations. Consequently, system weaknesses can be overcome with cooperation, but drivers should be assisted by an adaptive system.

High degrees of interaction fidelity (IF) in virtual reality (VR) are said to improve user experience and immersion, but there is also evidence of low IF providing comparable experiences. VR games are now increasingly prevalent, yet we still do not fully understand the trade-off between realism and abstraction in this context. We conducted a lab study comparing high and low IF for object manipulation tasks in a VR game. In a second study, we investigated players' experiences of IF for whole-body movements in a VR game that allowed players to crawl underneath virtual boulders and "dangle'' along monkey bars. Our findings show that high IF is preferred for object manipulation, but for whole-body movements, moderate IF can suffice, as there is a trade-off with usability and social factors. We provide guidelines for the development of VR games based on our results.

When player skill levels are not matched, games provide an unsatisfying player experience. Player balancing is used across many digital game genres to address this, but has not been studied for co-located augmented reality (AR) tabletop games, where using boosts and handicaps can adjust for different player skill levels. In the setting of an AR table football game, we studied the importance of game balancing being triggered by the game system or the players, and whether player skill should be required to trigger game balancing. We implemented projected icons to prominently display game balancing mechanics in the AR table football game. In a within-subjects study (N=24), we found players prefer skill-based control over game balancing and that different triggers are perceived as having different fairness. Further, the study showed that even game balancing that is perceived as unfair can provide enjoyable game experiences. Based on our findings, we provide suggestions for player balancing in AR tabletop games.

Sound and virtual reality (VR) are two important output modalities for creating an immersive player experience (PX). While prior research suggests that sounds might contribute to a more immersive experience in games played on screens and mobile displays, there is not yet evidence of these effects of sound on PX in VR. To address this, we conducted a within-subjects experiment using a commercial horror-adventure game to study the effects of a VR and monitor-display version of the same game on PX. Subsequently, we explored, in a between-subjects study, the effects of audio dimensionality on PX in VR. Results indicate that audio has a more implicit influence on PX in VR because of the impact of the overall sensory experience and that audio dimensionality in VR may not be a significant factor contributing to PX. Based on our findings and observations, we provide five design guidelines for VR games.

The adoption of virtual reality in various industrial sectors other than gaming is spreading by the day. Many people are still sceptical regarding the potentials and advantages of virtual reality because this has not been made obvious enough to convince them. We investigated how virtual reality affects the concentration, involvement and enjoyment of users during evaluation sessions. Eighty four participants drove on a virtual automated driving simulator with and without the Oculus rift CV1. The experiment showed a statistically significant result for all variables that virtual reality enables better concentration, better involvement and enjoyment when compared with conventional displays.

Entertainment and in particular gaming is currently considered one of the main application scenarios for virtual reality (VR). The majority of current games rely on any form of locomotion through the virtual environment while some techniques can lead to simulator sickness. Game developers are currently implementing a wide variety of locomotion techniques to cope with simulator sickness (e.g. teleportation). In this work we implemented and evaluated four different controller-based locomotion methods that are popular in current VR games (free teleport, fixpoint teleport, touchpad-based, automatic). We conducted a user study (n = 24) in which participants explored a virtual zoo with these four different controller-based locomotion methods and assessed their effects on discomfort, presence, enjoyment, and affective state. The results of our study show that free teleport locomotion elicited least discomfort and provided the highest scores for enjoyment, presence, and affective state. With these results we gained valuable insights for developers and researchers implementing first person locomotion in VR experiences.

Home automation faces the challenge of providing ubiquitous, unobtrusive services while empowering users with approachable configuration interfaces. These interfaces need to provide sufficient expressiveness to support complex automation, and notations need to be devised that enable less tech-savvy users to express such scenarios. Rule-based and process-oriented paradigms have emerged as opposing ends of the spectrum; however, their underlying concepts have not been studied comparatively. We report on a contextual inquiry study in which we collected qualitative data from 18 participants in 12 households on the current potential and acceptance of home automation, as well as explored the respective benefits and drawbacks of these two notation paradigms for end users. Results show that rule-based notations are sufficient for simple automation tasks but not flexible enough for more complex use cases. The resulting insights can inform the design of interfaces for smart homes to enable usable real-world home automation for end users.

Although there are already fully autonomous vehicles on the roads for testing purposes, a rollout is far away. Autonomous vehicles are still not able to handle everyday driving and remain reliant on the driver when they reach their system limitations. One suggested approach to this problem is handing over the control entirely to the driver, which might become annoying when such situations occur frequently. In contrast, we suggest the usage of cooperative interfaces to avoid full handovers in situations in which the system needs the driver, for instance to approve or monitor a specific maneuver. A driving simulator study with 32 participants revealed that they felt comfortable choosing how the system should handle a situation. They reportedly assessed the situations first instead of relying blindly on the system and were able to handle every situation safely. We report lessons learned regarding cooperative interaction and interfaces, and their in-lab evaluation.

Modern technical devices are often too complex for many users to be able to use them to their full extent. Based on planning technology, we are able to provide advanced user assistance for operating technical devices. We present a system that assists a human user in setting up a complex home theater consisting of several HiFi devices. For a human user, the task is rather challenging due to a large number of different ports of the devices and the variety of available cables. The system supports the user by giving detailed instructions how to assemble the theater. Its performance is based on advanced user-centered planning capabilities including the generation, repair, and explanation of plans.

Self-driving vehicles are able to drive on their own as long as the requirements of their autonomous systems are met. If the system reaches the boundary of its capabilities, the system has to de-escalate (e.g. emergency braking) or hand over control to the human driver. Accordingly, the design of a functional handover assistant requires that it enable drivers to both take over control and feel comfortable while doing so -- even when they were "out of the loop" with other tasks. We introduce a process to hand over control from a full self-driving system to manual driving, and propose a number of handover implementation strategies. Moreover, we designed and implemented a handover assistant based on users' preferences and conducted a user study with 30 participants, whose distraction was ensured by a realistic distractor task. Our evaluation shows that car-driver handovers prompted by multimodal (auditory and visual) warnings are a promising strategy to compensate for system boundaries of autonomous vehicles. The insights we gained from the take-over behavior of drivers led us to formulate recommendations for more realistic evaluation settings and the design of future handover assistants.

Recent trends in human–computer interaction (HCI) show a development towards cognitive technical systems (CTS) to provide natural and efficient operating principles. To do so, a CTS has to rely on data from multiple sensors which must be processed and combined by fusion algorithms. Furthermore, additional sources of knowledge have to be integrated, to put the observations made into the correct context. Research in this field often focuses on optimizing the performance of the individual algorithms, rather than reflecting the requirements of CTS. This paper presents the information fusion principles in CTS architectures we developed for Companion Technologies. Combination of information generally goes along with the level of abstractness, time granularity and robustness, such that large CTS architectures must perform fusion gradually on different levels — starting from sensor-based recognitions to highly abstract logical inferences. In our CTS application we sectioned information fusion approaches into three categories: perception-level fusion, knowledge-based fusion and application-level fusion. For each category, we introduce examples of characteristic algorithms. In addition, we provide a detailed protocol on the implementation performed in order to study the interplay of the developed algorithms.

In recent years, the automobile has become more connected and has started offering drivers a variety of services and applications for in-car use, such as Facebook, Twitter, and mobile payment. Many such services require user authentication. We have investigated the requirements and potential of authenticating users with a rotary control knob, which constitutes the central control entity (CCE) in many modern cars. In a user-centered design approach we adapted three established authentication schemes for in-car usage with consideration to driver distraction. We performed extensive user experiments in a driving simulator focusing on usability, security and driver distraction. The results of our experiments provide relevant insights for integrating user authentication methods into the automotive context solely based on present hardware components.

This paper is the first to assess the impact of touchscreen damage on smartphone interaction. We gathered a dataset consisting of 95 closeup images of damaged smartphones and extensive information about a device's usage history, damage severity, and impact on use. 88% of our participants continued to use their damaged smartphone for at least three months; 32% plan to use it for another year or more, mainly due to high repair and replacement costs. From the dataset, we identified three categories of damaged smartphone displays. Reading and text input were most affected. Further interviews (n=11) revealed that users adapt to damage with diverse coping strategies, closely tailored to specific interaction issues. In total, we identified 23 different strategies. Based on our results, we proposed guidelines for interaction design in order to provide a positive user experience when display damage occurs.

In this paper we describe a PhD research plan which focuses on the problem of insular thinking in distributed software development projects and its implications. The objective is to break up insular thinking in distributed agile software development through the targeted application of different media. The result of this work will be a model for distributed agile release planning. We intend to improve agile distributed release planning through the application of this model. Selected parts of the model will be evaluated through a software prototype which uses data of the Ice Breaker System project.

PriCal is an ambient calendar display that shows a user's schedule similar to a paper wall calendar. PriCal provides context-adaptive privacy to users by detecting present persons and adapting event visibility according to the user's privacy preferences. We present a detailed privacy impact assessment of our system, which provides insights on how to leverage context to enhance privacy without being intrusive. PriCal is based on a decentralized architecture and supports the detection of registered users as well as unknown persons. In a three-week deployment study with seven displays, ten participants used PriCal in their real work environment with their own digital calendars. Our results provide qualitative insights on the implications, acceptance, and utility of context-adaptive privacy in the context of a calendar display system, indicating that it is a viable approach to mitigate privacy implications in ubicomp applications.

Multimodal systems still tend to ignore the individual input behavior of users, and at the same time, suffer from erroneous sensor inputs. Although many researchers have described user behavior in specific settings and tasks, little to nothing is known about the applicability of such information, when it comes to increase the robustness of a system for multimodal inputs. We conducted a gamified experimental study to investigate individual user behavior and error types found in an actually running system. It is shown, that previous ways of describing input behavior by a simple classification scheme (like simultaneous and sequential) are not suited to build up an individual interaction history. Instead, we propose to use temporal distributions of different metrics derived from multimodal event timings. We identify the major errors that can occur in multimodal interactions and finally show how such an interaction history can practically be applied for error detection and recovery. Applying the proposed approach to the experimental data, the initial error rate is reduced from 4.9% to a minimum of 1.2%.

The properties of multimodality, individuality, adaptability, availability, cooperativeness and trustworthiness are at the focus of the investigation of Companion Systems. In this article, we describe the involved key components of such a system and the way they interact with each other. Along with the article comes a video, in which we demonstrate a fully functional prototypical implementation and explain the involved scientific contributions in a simplified manner. The realized technology considers the entire situation of the user and the environment in current and past states. The gained knowledge reflects the context of use and serves as basis for decision-making in the presented adaptive system.

Present context-aware systems gather a lot of information to maximize their functionality but they predominantly use rather static ways to communicate. This paper motivates two components that serve as mediators between arbitrary components for multimodal fission and fusion, aiming to improve communication skills. Along with an exemplary selection scenario we describe the architecture for an automatic cooperation of fusion and fission in a model-driven realization. We describe how the approach supports user-initiative dialog requests as well as user-nominated UI configuration. Despite that, we show how multimodal input conflicts can be solved using a shortcut in the commonly used human-computer interaction loop (HCI loop).

While privacy is often treated as an information centric issue, privacy issues in ubiquitous and mobile computing also encompass physical or territorial aspects, i.e., the right to be left alone or undisturbed. Disturbances that affect privacy often stem from persons nearby and their mobile devices, e.g., ringing phones, loud phone calls, or sounds of mobile games. We propose PriPref Broadcaster, a smartphone-based approach for communicating personal privacy preferences to persons in physical proximity. Our approach further supports automatic adaptation of mobile device settings based on the dominating preferences in the current environment. Results from a usability study and a five-day field trial with 28 participants show that broadcasting privacy preferences is perceived as meaningful and has the potential to support privacy signaling in many everyday situations.

Mobile Internet access via smartphones puts demands on in-car infotainment sys-tems, as more and more drivers like to ac-cess the Internet while driving. Spoken dialog systems (SDS) distract drivers less than visual/haptic-based dialog systems. However, in conversational SDSs drivers might speak utterances which are not in the domain of the SDS and thus cannot be understood. In a Wizard of Oz study, we evaluate the effects of out-of-domain utterances on cognitive load, driving per-formance, and usability. The results show that an SDS which reacts as expected by the driver, is a good approach to control in-car infotainment systems, whereas unex-pected SDS reactions might cause severe accidents. We evaluate how a dialog initia-tive switch, which guides the user and en-ables him to reach his task goal, performs. 1

Searching for misplaced keys, phones, or wallets is a common nuisance. Find My Stuff (FiMS) provides search support for physical objects inside furniture, on room level, and in multiple locations, e.g., home and office. Stuff tags make objects searchable while all other localization components are integrated into furniture. FiMS requires minimal configuration and automatically adapts to the user's furniture arrangement. Object search is supported with relative position cues, such as "phone is inside top drawer" or "the wallet is between couch and table," which do not require exact object localization. Functional evaluation of our prototype shows the approach's practicality with sufficient accuracy in realistic environments and low energy consumption. We also conducted two user studies, which showed that objects can be retrieved significantly faster with FiMS than manual search and that our relative position cues provide better support than map-based cues. Combined with audiovisual feedback, FiMS also outperforms spotlight-based cues.

Zero configuration networking aims to support users in seamlessly connecting devices and services. However, in public networks associated service announcements pose substantial privacy risks. A major issue is the inclusion of identifying information in device names, often automatically set or suggested by devices upon initial configuration. Focusing on mDNS, we assess this issue by studying its actual extent, awareness about the problem, and potential consequences for privacy. We collected a one-week dataset of mDNS announcements in a semi-public Wi-Fi network at a university. Of 2,957 unique device names, 59% contained real names of users, with 17.6% containing first and last name. An online survey (n=137) revealed that 29% of the participants did not know the current device name of their smartphone, but that the vast majority considered periodic announcement of their full names worrisome. We further discuss specific potential privacy threats and attack scenarios stemming from mDNS device names.

Smartphones have emerged as a likely application area for graphical passwords, because they are easier to input on touchscreens than text passwords. Extensive research on graphical passwords and the capabilities of modern smartphones result in a complex design space for graphical password schemes on smartphones. We analyze and describe this design space in detail. In the process, we identify and highlight interrelations between usability and security characteristics, available design features, and smartphone capabilities. We further show the expressiveness and utility of the design space in the development of graphical passwords schemes by implementing five different existing graphical password schemes on one smartphone platform. We performed usability and shoulder surfing experiments with the implemented schemes to validate identified relations in the design space. From our results, we derive a number of helpful insights and guidelines for the design of graphical passwords.

Automotive navigation systems are becoming ubiquitous as driver assistance systems. Vendors continuously aim to enhance route guidance by adding new features to their systems. However, we found in an analysis of current navigation systems that many share interaction weaknesses, which can damage the system’s credibility. Such issues are most prevalent when selecting a route, deviating from the route intentionally, or when systems react to dynamic traffic warnings. In this work, we analyze the impact on credibility and propose improved interaction mechanisms to enhance perceived credibility of navigation systems. We improve route selection and the integration of dynamic traffic warnings by optimizing route comparability with relevance-based information display. Further, we show how bidirectional communication between driver and device can be enhanced to achieve a better mapping between device behavior and driver intention. We evaluated the proposed mechanisms in a comparative user study and present results that confirm positive effects on perceived credibility.

The increasing ubiquity of mobile handheld devices paved the way for the dynamic ridesharing which could save travel cost and reduce the environmental pollution. The ridematching problem with time windows in dynamic ridesharing considers matching drivers and riders with similar routes (with drivers detour flexibility) and time schedules on short notice. This problem is hard to solve. In this work, we model the ridematching problem with time windows in dynamic ridesharing as an optimization problem and propose a genetic algorithm to solve it. We consider minimizing the total travel distance and time of the drivers (vehicles) and the total travel time of the riders and maximizing the number of the matches. In addition, we provide datasets for the ridematching problem, derived from a real world travel survey for northeastern Illinois, to test the proposed algorithm. Experimentation results indicate that the idea of dynamic ridesharing is feasible and the proposed algorithm is able to solve the ridematching problem with time windows in reasonable time.

The multiobjective time-dependent route planning problem is a hard multiobjective combinatorial optimization problem. Metaheuristics showed success in solving many hard optimization problems and recently many efforts have been directed to hybridize elements from different metaheuristics and search methods. The hybridization of genetic algorithms and local search methods proved to be successful in many domains. In this paper we present a genetic local search algorithm for solving the multiobjective time-dependent route planning problem taking the multiobjective route planning in dynamic multihop ridesharing as an example problem. The behavior of the proposed algorithm is compared, on two problem instances using a set of widely used quality indicators, with the behavior of a genetic algorithm proposed for solving the same problem. Experimentation results indicated that the proposed algorithm outperforms the genetic algorithm regarding all quality indicators.

In this paper, we address the dynamic ridematching problem with time windows in dynamic ridesharing. The dynamic ridesharing is a special type of ridesharing where the participants form ridesharing on short notice. The ridematching problem is to assign riders to drivers and to define the ordering and timing of the riders' pickup and delivery. Because not all information is known in advance, the problem is dynamic. This is an optimization problem where we optimize a multicriteria objective function. We consider minimizing the total travel distance and time of the drivers and the total travel time of the riders and maximizing the number of the transported riders.

Ubiquitous computing is characterized by the merger of physical and virtual worlds as physical artifacts gain digital sensing, processing, and communication capabilities. Maintaining an appropriate level of privacy in the face of such complex and often highly dynamic systems is challenging. We argue that context awareness not only enables novel UbiComp applications but can also support dynamic regulation and configuration of privacy mechanisms. We propose a higher level context model that abstracts from low level details and contains only privacy relevant context features. Context changes in our model can trigger reconfiguration of privacy mechanisms or facilitate context-specific privacy recommendations to the user. Based on our model, we analyze potential privacy implications of context changes and discuss how these results could inform actual reconfiguration of privacy mechanisms.

In ridesharing systems, drivers and riders decide to share their trips with each other for cost sharing, fun, reducing congenstion, etc. The ride matching problem with time windows consists of matching a set of drivers' offers and a set of riders' requests based on their sources, destinations and timing with detour willingness. If a request can be matched with only one offer, then the problem is called single hop ride matching. It is called multihop ride matching, if a request can be matched with two offers at different times. In this work, we model the multihop ride matching problem with time windows and provide a genetic algorithm to solve it. Experimentation results on a realistic dataset indicate that the multihop ride matching could increase the number of matched requests as compared with single hop ride matching.

To fully utilize the social potential of virtual environments, support for seamless and automatic integration of nonverbal communication is essential. In this paper we propose a conceptual and architectural design for a framework, which provides an integrated, flexible environment for the cooperation of heterogeneous modules specialized in different aspects of the acquirement, analysis and presentation of nonverbal communication cues. We propose a semantic framework for the knowledge exchange between these modules, as well as a general purpose architecture for the semantically correct fusion of nonverbal features.

Searching for lost keys, wallets or mobile phones is a common nuisance. Compared to digital information, search support for physical objects is very limited. We propose Find My Stuff (FiMS) as a search engine for physical objects. We built a fully functional Arduino-based prototype. FiMS offers the users a simple search interface to locate tagged physical items in different indoor environments. A hierarchical search process ensures energy efficient and effective searches. Instead of a fixed search infrastructure, the localization system is based on SmartFurniture equipped with RFID readers and ZigBee modules. Search results provide intuitive search cues based on relative positioning to support users in the physical retrieval of their lost objects. The system requires no manual calibration and is robust against rearrangement of SmartFurniture. Safety mechanisms prevent abuse of the system and protect user privacy.

Virtual keyboards of different smartphone platforms seem quite similar at first glance, but the transformation from a physical to a virtual keyboard on a small-scale display results in user experience variations that cause significant differences in usability as well as shoulder surfing susceptibility, i.e., the risk of a bystander observing what is being typed. In our work, we investigate the impact of both aspects on the security of text-based password entry on mobile devices. In a between subjects study with 80 participants, we analyzed usability and shoulder surfing susceptibility of password entry on different mobile platforms (iOS, Android, Windows Phone, Symbian, MeeGo). Our results show significant differences in the usability of password entry (required password entry time, typing accuracy) and susceptibility to shoulder surfing. Our results provide insights for security-aware design of on-screen keyboards and for password composition strategies tailored to entry on smartphones.

Telematics applications in automobiles have attracted considerable attention for their promise of value-added services. However, new challenges arise from the integration of telematics applications that require a multitude of vehicular data. The safety-critical context of the automotive domain calls for reliable access control mechanisms, especially when applications access sensitive data. However, those mechanisms must also respect the requirement of minimal driver distraction. To cope with these issues we propose Ginger -- an access control framework for telematics applications. Ginger is context aware, provides enhanced privacy protection, and realizes advanced access control paradigms. We demonstrate Ginger's feasibility with an Android-based implementation in a functional evaluation consisting of two representative use cases and in a comparative analysis with related approaches.

Ridesharing is considered as one of the promising solutions for dropping the consumption of fuel and reducing the congestion in urban cities, hence reducing the environmental pollution. Route planning is a key component for the success of ridesharing systems in which multiple objectives can be optimized. The multiobjective route planning problem in multi hop ridesharing is categorized as NP-complete. Multiobjective evolutionary algorithms have received a growing interest in solving the multiobjective optimization problems. In this work, we compare the behaviour of different multiobjective evolution ary algorithms for solving the multiobjective route planning in dynamic multi-hop ridesharing. Comparison results indicate that there is no single algorithm, as in literature, that wins all the tournaments regarding all the quality indicators. However, a subset of the algorithms is recommended with better quality and runtime.

Support vector machines (SVMs) often contain a large number of support vectors which reduce the run-time speeds of decision functions. In addition, this might cause an over fitting effect where the resulting SVM adapts itself to the noise in the training set rather than the true underlying data distribution and will probably fail to correctly classify unseen examples. To obtain more fast and accurate SVMs, many methods have been proposed to prune SVs in trained SVMs. In this paper, we propose a multi-objective genetic algorithm to reduce the complexity of support vector machines as well as to improve generalization accuracy by the reduction of over fitting. Experiments on four benchmark datasets show that the proposed evolutionary approach can effectively reduce the number of support vectors included in the decision functions of SVMs without sacrificing their classification accuracy.

The multiobjective route planning problem in dynamic multi-hop ridesharing is considered to be NP-complete. Evolutionary computation has received a growing interest in solving the hard multiobjective optimization problems. In this study we investigate the behavior of different variants of the ant colony based approach for solving the multiobjective route planning problem and compare the performance of the different variants with the performance of a genetic algorithm recommended for solving the problem. Experimentation results indicate that the ant colony approach encounters poor performance in its native form and competes the genetic approach in some of its variants when combined with local search.

The Multifunctional and Adaptive Meal Preparation Facility (MAMPF) is a versatile and adaptive kitchen system allowing even an inexperienced user to create ambitious dishes. On the hardware side, the system controls hotplates by regulating the temperature of heated regions to turn the attention to the food actually being heated instead of the hotplate. Furthermore, the user interaction with the computer system is adapted to the requirements in a kitchen. On the work flow side, MAMPF converts a recipe into a task tree which is used to guide the user through the cooking process. By knowing the recipe, based on a formal description specially developed for this system, the optimal sequence of actions can be calculated. The system is designed to support the user without limiting spontaneity or creativity and can - if necessary - be used just like any usual stove. Consequentially, the user always retains control over the system, all settings can be overwritten at any point, and the order of the tasks can be dynamically rearranged. In order to prove the correctness of this concept, a prototype has been implemented.

Automotive navigation systems, especially portable navigation devices (PNDs), are gaining popularity worldwide. Drivers increasingly rely on these devices to guide them to their destination. Some follow them almost blindly, with devastating consequences if the routing goes wrong. Wrong messages as well as superfluous and unnecessary messages can potentially reduce the credibility of those devices. We performed a comparative study with current PNDs from different vendors and market segments, in order to assess the extent of this problem and how it is related to the interaction between device and driver. In this paper, we report the corresponding results and identify multiple interaction weaknesses that are prevalent throughout all tested device classes.

Privacy is an important requirement in vehicle networks, because vehicles broadcast detailed location information. Also of importance is accountability due to safety critical applications. Conditional pseudonymity, i.e., usage of resolvable pseudonyms, is a common approach to address both. Often, resolvability of pseudonyms is achieved by authorities maintaining pseudonym- identity mappings. However, these mappings are privacy sensitive and require strong protection to prevent abuse or leakage. We present a new approach that does not rely on pseudonym-identity mappings to be stored by any party. Resolution information is directly embedded in pseudonyms and can only be accessed when multiple authorities cooperate. Our privacy-preserving pseudonym issuance protocol ensures that pseudonyms contain valid resolution information but prevents issuing authorities from creating pseudonym-identity mappings.

In this paper we present an approach for creating user interfaces from abstract representations for the automotive domain. The approach is based on transformations between different user interface abstraction levels. Existing user interface representation methods are presented and evaluated. The impact of specific requirements for automotive human-machine interaction is discussed. Considering these requirements a process based on transformation rules is outlined to allow for flexible integration of external infotainment applications coming from mobile devices or web sources into the in-car interaction environment.

With the FreeMote system, we present a solution for easy and intuitive universal device control. Based on the Wii Remote Controller real world device functions can be accessed and controlled via gestures. Gestures include predefined sets apt for standard functions present in many devices as well as user definable gestures. Offering both possibilities, the users are free to choose and adapt the gestures to their needs while reducing the mental load. Along with the gesture interface, FreeMote offers a simple way of enabling everyday devices for FreeMote controlling. FreeMote makes use of the spatial nature of real world environments in device selection and in function controlling via gestures. Thus, FreeMote system supports the user in finding enabled devices, makes selecting devices easy and provides an intuitive way of controlling devices via gestures.

Vehicle-to-vehicle/vehicle-to-infrastructure (V2X) communication systems are envisioned to greatly improve road safety, traffic efficiency, and driver convenience. However, many V2X applications rely on continuous and detailed location information, which raises location privacy concerns. A multitude of privacy-protection mechanisms have been proposed in recent years. However, few efforts have been made to develop privacy metrics, which can provide a rigorous way to assess the privacy risk, evaluate the effectiveness of a given mechanism, and exploit the full possibilities of protection methods in V2X systems. Therefore, in this paper we present a trip-based location privacy metric for measuring user location privacy in V2X systems. The most distinguishable aspect of the metric is to take into account the accumulated information, which is the privacy-related information acquired by an adversary for an extended period of time, e.g., days or weeks. We develop methods to model and process the accumulated information, and reflect the impact on the privacy level in the metric. We further prove the viability and correctness of the metric by various case studies. Our simulations find out that under certain conditions, accumulated information can significantly decrease the level of user location privacy. The metric and our findings in this paper give some valuable insights into location privacy, which can contribute to the development of effective privacy-protection mechanisms for the users of V2X systems.

Efficient information dissemination is one of the challenging tasks in most ad-hoc network application domains, be it in wireless sensor networks, mobile ad-hoc networks, or vehicular ad-hoc networks. It is obvious, that flooding has a high communication overhead, leading to channel congestion and packet collisions. Therefore, more efficient dissemination mechanisms were investigated and proposed by the research community. One class of such algorithms is gossiping, where each node forwards a message with a certain probability. The main challenge in gossiping is the proper determination of the forwarding probability, i.e., on the one hand this value has to be chosen high enough to assure a high delivery ratio, on the other hand it has to be as low as possible to reduce communication overhead. At the same time this probability has to be adapted to dynamic network conditions, like changing node density. In this work an advanced scheme for adaptive gossiping is proposed, capable to adjust the dissemination probability dynamically and in a distributed manner. The gossiping probability is determined at a node for every message that has to be forwarded based on two hop neighborhood information. That way, the proposed protocol is capable of working in arbitrary network topologies and densities, enabling more efficient data dissemination compared to existing approaches.

Most techniques for personal data synchronization only allow one-to-one or star network topologies. Enkel DS presented in this paper extends OMA SyncML DS, an open industry standard for optimistic data synchronization. Enkel DS allows many-to-many topologies including cycles enabling a human user to synchronize each personal device with another.

Mechanisms for information dissemination are essential for many applications in vehicular ad-hoc networks (VANETs). Currently, simple flooding is often supposed to broadcast information within a geographic region, as for example in many geocast protocols. However, simple flooding has several drawbacks: every node rebroadcasting a message leads to redundancy, contention, and collision, to which is referred as the broadcast storm problem. Hence, in order to fulfill the applications' requirements, more efficient solutions are necessary. In this work we introduce three extensions to an existing probabilistic broadcast protocol to be capable to achieve high reception rates with a wide range of vehicle densities, at the same time lowering the communication complexity. The efficiency of the protocol is shown by simulations in an intersection and highway scenario and its superiority over flooding and the basic protocol is presented.

Pseudonyms are pseudonymous certificates, which are regarded as a silver bullet to meet the security and privacy requirements of vehicular communications. Most works so far assume that pseudonyms are readily available when they are needed. In this paper, we identify and compare two strategies to refill pseudonyms. We then propose the pseudonym-on-demand scheme, which is an implementation of one of the strategies. We show that our approach supports the functionalities of pseudonyms in terms of secure and privacy-preserved vehicular communications. Furthermore, our proposed scheme serves as a platform, into which many features to enhance security and privacy can be integrated.

This paper has shown that U2VAS fulfills all requirements of a truly modular and flexible communication stack for VANETs. Beyond the framework, the current implementation already contains several forms of communication, positioning and security mechanisms. We invite interested developers to join our effort and contribute to the further development of U2VAS.

Abstract Information dissemination rather than traditional routing is useful for many application domains in mobile ad hoc networks. Context‐adaptive information dissemination is a special variant, which was originally designed for vehicular ad hoc networks (VANETs), but could also be used in other domains, for example, disaster management. In this work, we address the security of this dissemination scheme. The attack analysis shows weaknesses but also how the adaption to context already limits the impact of many attacks. We present and evaluate a sensor‐based protection system helping to reduce the margin for attacks to a level of local disturbance, while the overall dissemination is not affected significantly any more. Copyright © 2008 John Wiley & Sons, Ltd.

The privacy aspect is often neglected in many electronic systems. With the emergence of ubiquitous systems, privacy will become an even more important aspect than it has been in the past. Location privacy - the information where exactly a node is currently located - is one aspect. This paper classifies several kinds of attacks on location privacy. It examines the results of these attacks on a scheme utilising changing identities to preserve the users’ identities. Simulation results show the influence of the number of nodes and the backoff time between transmissions on the nodes’ location privacy.

The authors discuss the structure of training cases in Web based and case-oriented training systems. We combine the benefits of systems that support a structural representation of knowledge underlying a training case and those that allow a fine granularity of didactical aspects. Our results emerged from the development of a training system in medicine, "Docs 'n Drugs-The Virtual Polyclinic" (T. Illmann et al., 2000). The abstraction from the proposed training case structure offers a good basis for general case oriented training systems, an easy exchange of tutoring data, and the Web based indexing of learning material.

Recently many prominent web sites face so called Distributed Denial of Service Attacks (DDoS). While former security threats could be faced by a tight security policy and active measures like using rewalls, vendor patches etc. these DDoS are new in suchway that there is no completely satisfying protection yet. In this paper we categorize different forms of attacks and give an overview over the most common DDoS tools. Furthermore we present a solution based on Class Based Routing mechanisms in the Linux kernel that will prevent the most severe impacts of DDoS on clusters of web servers with a prepended load balancing server. The goal is to keep the web servers under attack responding to the normal client requests. Some performance tests and a comparison to other approaches conclude our paper.

Telecooperation receives increasing importance in a globalized information and work infrastructure. Among others, teleconferencing and workflow management are technological areas being studied and developed to support telecooperation scenarios. i.e. real-time collaboration tasks are being supported by teleconferencing systems, asynchronous tasks are being supported by workflow management systems. An integrated telecooperation framework for both approaches is described, which uses a conference broker to couple both system types. The close coupling, however, is not transparent with respect to the actual instances of used systems. This lack of service selection transparency also results in a lack of location transparency. Thus, the authors extend their framework by a trading service. Workflow modules act as the importers of teleconferencing services being exported by conference modules. A distributed trading service mediates between service offers and service requests. The trader is self-sufficient as it does not require any distributed platform, such as CORBA or DCE. It may be deployed in a standard Internet infrastructure.

Two different areas of distributed group work are supported by workflow management systems and real-time collaboration systems. Workflow management systems support work being structured in steps such that each step can be handled with the results of former steps and the expertise of the person working on that step. On the other hand, multimedia collaboration systems are best suited for unstructured group activities. Audiovisual connectivity and shared documents enable flexible group processes. All coordination tasks are left to the conference participants. This paper introduces an integration concept and prototype system which combines the advantages of both types of CSCW-systems. Keywords Workflow Management, Teleconferencing, Conference Assistant, Brokerage, Trading INTRODUCTION AND MOTIVATION Due to the ongoing globalization many companies are forced to decentralize their organizational structures. This requires an orientation towards business processes derived from an entire vi...