Enabling Social Applications via Decentralized Social Data Management

An unprecedented information wealth produced by online social networks, further augmented by location/collocation data, is currently fragmented across different proprietary services. Combined, it can accurately represent the social world and enable novel socially-aware applications. We present Prometheus, a socially-aware peer-to-peer service that collects social information from multiple sources into a multigraph managed in a decentralized fashion on user-contributed nodes, and exposes it through an interface implementing non-trivial social inferences while complying with user-defined access policies. Simulations and experiments on PlanetLab with emulated application workloads show the system exhibits good end-to-end response time, low communication overhead and resilience to malicious attacks.Comment: 27 pages, single ACM column, 9 figures, accepted in Special Issue of Foundations of Social Computing, ACM Transactions on Internet Technolog

An Investigation of Legal and Ethical Issues with User-Generated Content and Other Forms of Electronically Stored Information Communicated via Social Media, Messaging Apps and Social Devices, Including the Internet of Things

On social networking services, sharing is caring. However, depending on who or what is involved, sharing can be the source of a community transgression, copyright infringement, a violation of employment policies or worse. If people who use social media, mobile messaging apps and social devices do not know where the ethical or legal lines are drawn, in jurisprudence, in vendor Terms of Service, in professional codes of conduct or in keeping with online social norms, they are in jeopardy of being publicly shamed or even sued. Users may also put their employers, friends and colleagues at risk of community, professional or legal penalties in an era where the boundary between work and leisure is becoming even more blurred. This mixed-methods, interdisciplinary research project explores the current state of awareness on a range of legal and ethical issues involving User-Generated Content (UGC) and other forms of Electronically Stored Information (ESI) on social networks and devices for personal and enterprise use and for several different constituencies, including marketers, artists, journalists, academics, educators, entrepreneurs, bloggers, photographers and videographers. The quantitative, numeric data resulting from an online survey as well as qualitative, descriptive data gathered from semi-structured interviews with participants and observations gleaned in contextual inquiry will help address gaps in current research on this subject. In addition, the research findings will guide design directions for a tool, intervention or affordance to help users become better informed about privacy, intellectual property and information governance in the context of electronic sharing and more easily put this knowledge into practice. The first phase of developing the survey protocol is already underway, with a literature review completed and the survey submitted for IRB review as #1602921512. Pilot contextual inquiries and field studies are being pursued to guide development of qualitative research phases in the future. 1. Bohn, J., et al. Social, economic, and ethical implications of ambient intelligence and ubiquitous computing. Ambient Intelligence. Springer Berlin Heidelberg, 2005, 5-29. 2. Cohen, J.E. Configuring the Networked Self: Law, Code, and the Play of Everyday Practice. Yale University Press, 2012. 3. Erickson, T., and Kellogg, W.A. Social translucence: an approach to designing systems that support social processes. ACM Transactions on Computer-Human Interaction (TOCHI) 7.1 (2000): 5983. 4. Faklaris, C., and Hook, S.A. Oh, Snap! The State of Electronic Discovery Amid the Rise of Snapchat, WhatsApp, Kik and Other Mobile Messaging Apps. Federal Lawyer, May 2016 [in press]. 5. Fiesler, C., and Bruckman, A.S. Remixers' understandings of fair use online. Proceedings of the 17th ACM Conference on Computer Supported Cooperative Work and Social Computing. ACM, 2014. 6. Hook, S.A., and Faklaris, C. Social Media, The Internet and Electronically Stored Information (ESI) Challenges. National Business Institute, 2015. Available at https://scholarworks.iupui.edu/handle/1805/7177

Quality of Information in Mobile Crowdsensing: Survey and Research Challenges

Smartphones have become the most pervasive devices in people's lives, and are clearly transforming the way we live and perceive technology. Today's smartphones benefit from almost ubiquitous Internet connectivity and come equipped with a plethora of inexpensive yet powerful embedded sensors, such as accelerometer, gyroscope, microphone, and camera. This unique combination has enabled revolutionary applications based on the mobile crowdsensing paradigm, such as real-time road traffic monitoring, air and noise pollution, crime control, and wildlife monitoring, just to name a few. Differently from prior sensing paradigms, humans are now the primary actors of the sensing process, since they become fundamental in retrieving reliable and up-to-date information about the event being monitored. As humans may behave unreliably or maliciously, assessing and guaranteeing Quality of Information (QoI) becomes more important than ever. In this paper, we provide a new framework for defining and enforcing the QoI in mobile crowdsensing, and analyze in depth the current state-of-the-art on the topic. We also outline novel research challenges, along with possible directions of future work.Comment: To appear in ACM Transactions on Sensor Networks (TOSN

Gunrock: GPU Graph Analytics

For large-scale graph analytics on the GPU, the irregularity of data access and control flow, and the complexity of programming GPUs, have presented two significant challenges to developing a programmable high-performance graph library. "Gunrock", our graph-processing system designed specifically for the GPU, uses a high-level, bulk-synchronous, data-centric abstraction focused on operations on a vertex or edge frontier. Gunrock achieves a balance between performance and expressiveness by coupling high performance GPU computing primitives and optimization strategies with a high-level programming model that allows programmers to quickly develop new graph primitives with small code size and minimal GPU programming knowledge. We characterize the performance of various optimization strategies and evaluate Gunrock's overall performance on different GPU architectures on a wide range of graph primitives that span from traversal-based algorithms and ranking algorithms, to triangle counting and bipartite-graph-based algorithms. The results show that on a single GPU, Gunrock has on average at least an order of magnitude speedup over Boost and PowerGraph, comparable performance to the fastest GPU hardwired primitives and CPU shared-memory graph libraries such as Ligra and Galois, and better performance than any other GPU high-level graph library.Comment: 52 pages, invited paper to ACM Transactions on Parallel Computing (TOPC), an extended version of PPoPP'16 paper "Gunrock: A High-Performance Graph Processing Library on the GPU

Incentive Mechanisms for Participatory Sensing: Survey and Research Challenges

Participatory sensing is a powerful paradigm which takes advantage of smartphones to collect and analyze data beyond the scale of what was previously possible. Given that participatory sensing systems rely completely on the users' willingness to submit up-to-date and accurate information, it is paramount to effectively incentivize users' active and reliable participation. In this paper, we survey existing literature on incentive mechanisms for participatory sensing systems. In particular, we present a taxonomy of existing incentive mechanisms for participatory sensing systems, which are subsequently discussed in depth by comparing and contrasting different approaches. Finally, we discuss an agenda of open research challenges in incentivizing users in participatory sensing.Comment: Updated version, 4/25/201

Socializing the Semantic Gap: A Comparative Survey on Image Tag Assignment, Refinement and Retrieval

Where previous reviews on content-based image retrieval emphasize on what can be seen in an image to bridge the semantic gap, this survey considers what people tag about an image. A comprehensive treatise of three closely linked problems, i.e., image tag assignment, refinement, and tag-based image retrieval is presented. While existing works vary in terms of their targeted tasks and methodology, they rely on the key functionality of tag relevance, i.e. estimating the relevance of a specific tag with respect to the visual content of a given image and its social context. By analyzing what information a specific method exploits to construct its tag relevance function and how such information is exploited, this paper introduces a taxonomy to structure the growing literature, understand the ingredients of the main works, clarify their connections and difference, and recognize their merits and limitations. For a head-to-head comparison between the state-of-the-art, a new experimental protocol is presented, with training sets containing 10k, 100k and 1m images and an evaluation on three test sets, contributed by various research groups. Eleven representative works are implemented and evaluated. Putting all this together, the survey aims to provide an overview of the past and foster progress for the near future.Comment: to appear in ACM Computing Survey

Amplifying Quiet Voices: Challenges and Opportunities for Participatory Design at an Urban Scale

Many Smart City projects are beginning to consider the role of citizens. However, current methods for engaging urban populations in participatory design activities are somewhat limited. In this paper, we describe an approach taken to empower socially disadvantaged citizens, using a variety of both social and technological tools, in a smart city project. Through analysing the nature of citizens’ concerns and proposed solutions, we explore the benefits of our approach, arguing that engaging citizens can uncover hyper-local concerns that provide a foundation for finding solutions to address citizen concerns. By reflecting on our approach, we identify four key challenges to utilising participatory design at an urban scale; balancing scale with the personal, who has control of the process, who is participating and integrating citizen-led work with local authorities. By addressing these challenges, we will be able to truly engage citizens as collaborators in co-designing their city