With the widespread use of GPS-equipped smartphones and Internet of Things devices, a huge amount of data with location information is being generated at an unprecedented rate. To gain a deeper insight into such a plethora of spatial data, scientists and engineers are widely using spatial queries for their big data applications. However, because of not only the massive spatial data size but also the complexity of spatial query processing, they are struggling to efficiently process the spatial queries. In this paper, we propose lightweight and scalable indexing and querying services for big spatial data stored in distributed storage systems or graph-based systems. Our spatial services have several advantages over existing approaches. First, our services can be easily applied to existing storage systems or graph-based models without modifying the internal implementation of existing systems/models. Second, our services achieve high pruning power by efficiently selecting only relevant spatial objects based on a simple yet effective filter. Third, our services support a customizable and easy-to-use control of index data size by adjusting the precision of indexed geometries. Lastly, our services support efficient updates of spatial data. Our experimental results using real-world datasets validate the effectiveness and efficiency of our spatial services.

The abundance of available information on social media can provide invaluable insights into people’s responses to health information and public health guidance concerning COVID-19. This study examines tweeting patterns and public engagement on Twitter, as forms of social media, related to public health messaging in two U.S. states (Washington and Louisiana) during the early stage of the pandemic. We analyze more than 7M tweets and 571K COVID-19-related tweets posted by users in the two states over the first 25 days of the pandemic in the U.S. (Feb. 23, 2020, to Mar. 18, 2020). We also qualitatively code and examine 460 tweets posted by selected governmental official accounts during the same period for public engagement analysis. We use various methods for analyzing the data, including statistical analysis, sentiment analysis, and word usage metrics, to find inter- and intra-state disparities of tweeting patterns and public engagement with health messaging. Our findings reveal that users in Washington were more active on Twitter than users in Louisiana in terms of the total number and density of COVID-19-related tweets during the early stage of the pandemic. Our correlation analysis results for counties or parishes show that the Twitter activities (tweet density, COVID-19 tweet density, and user density) were positively correlated with population density in both states at the 0.01 level of significance. Our sentiment analysis results demonstrate that the average daily sentiment scores of all and COVID-19-related tweets in Washington were consistently higher than those in Louisiana during this period. While the daily average sentiment scores of COVID-19-related tweets were in the negative range, the scores of all tweets were in the positive range in both states. Lastly, our analysis of governmental Twitter accounts found that these accounts’ messages were most commonly meant to spread information about the pandemic, but that users were most likely to engage with tweets that requested readers take action, such as hand washing.

We present MobiMix, a road network based mix-zone framework to protect location privacy of mobile users traveling on road networks. An alternative and complementary approach to spatial cloaking based location privacy protection is to break the continuity of location exposure by introducing techniques, such as mix-zones, where no applications can trace user movements. However, existing mixzone proposals fail to provide effective mix-zone construction and placement algorithms that are resilient to timing and transition attacks. In MobiMix, mix-zones are constructed and placed by carefully taking into consideration of multiple factors, such as the geometry of the zones, the statistical behavior of the user population, the spatial constraints on movement patterns of the users, and the temporal and spatial resolution of the location exposure. In this demonstration, we first introduce a visualization of the location privacy risks of mobile users traveling on road networks and show how mixzone based anonymization breaks the continuity of location exposure to protect user location privacy. We demonstrate a suite of road network mix-zone construction and placement methods that provide higher level of resilience to timing and transition attacks on road networks. We show the effectiveness of the MobiMix approach through detailed visualization using traces produced by GTMobiSim on different scales of geographic maps.

Background: Long-read sequencing has shown the promises to overcome the short length limitations of second-generation sequencing by providing more complete assembly. However, the computation of the long sequencing reads is challenged by their higher error rates (e.g., 13% vs. 1%) and higher cost ($0.3 vs. $0.03 per Mbp) compared to the short reads.Methods: In this paper, we present a new hybrid error correction tool, called ParLECH (Parallel Long-read Error Correction using Hybrid methodology). The error correction algorithm of ParLECH is distributed in nature and efficiently utilizes thek-mer coverage information of high throughput Illumina short-read sequences to rectify the PacBio long-read sequences.ParLECH first constructs a de Bruijn graph from the short reads, and then replaces the indel error regions of the long reads with their corresponding widest path (or maximum min-coverage path) in the short read-based de Bruijn graph. ParLECH then utilizes thek-mer coverage information of the short reads to divide each long read into a sequence of low and high coverage regions, followed by a majority voting to rectify each substituted error base.Results: ParLECH outperforms latest state-of-the-art hybrid error correction methods on real PacBio datasets. Our experimental evaluation results demonstrate that ParLECH can correct large-scale real-world datasets in an accurate and scalable manner. ParLECH can correct the indel errors of human genome PacBio long reads (312 GB) with Illumina short reads (452 GB) in less than 29 h using 128 compute nodes. ParLECH can align more than 92% bases of anE. coliPacBio dataset with the reference genome, proving its accuracy.Conclusion: ParLECH can scale to over terabytes of sequencing data using hundreds of computing nodes. The proposed hybrid error correction methodology is novel and rectifies both indel and substitution errors present in the original long reads or newly introduced by the short reads.

In emerging information networks, having a privacy preserving index (or PPI) is critically important for locating information of interest for data sharing across autonomous providers while preserving privacy. An understudied problem for PPI techniques is how to provide controllable privacy preservation, given the innate difference of privacy concerns regarding different data owners. In this paper we present a personalized privacy preserving index, coined ε-PPI, which guarantees quantitative privacy preservation differentiated by personal identities. We devise a new common-identity attack that breaks existing PPI's and propose an identity-mixing protocol against the attack in ε-PPI. The proposed ε-PPI construction protocol is the first without any trusted third party and/or trust relationships between providers. We have implemented our ε-PPI construction protocol by using generic MPC techniques (secure multi-party computation) and optimized the performance to a practical level by minimizing the expensive MPC part.