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We present a scalable approach for identifying moving flock patterns in large trajectory databases. A moving flock pattern refers to a group of entities that move closely together within a defined spatial radius for a minimum time interval. We focus on improving the state-of-the-art sequential algorithms, which suffer from high computational costs when dealing with large datasets. By leveraging distributed frameworks and utilizing spatial partitioning, the proposed solution aims to significantly reduce the time required to detect moving flock patterns. We highlight the bottlenecks of the sequential approaches and offer optimizations like partition-based parallelism and strategies for managing flock patterns that span multiple partitions. An experimental evaluation using synthetic trajectory datasets, demonstrates that the proposed methods substantially improve scalability and performance compared to existing sequential algorithms. 

Abstract The Doubly Connected Edge List (DCEL) is an edge-list structure widely used in spatial applications, primarily for planar topological and geometric computations. However, it is also applicable to various types of data, including 3D models and geographic data. An essential operation is theoverlay operation, which combines the DCELs of two input polygon layers and can easily support spatial queries on polygons like the intersection, union, and difference between these layers. However, existing techniques for spatial overlay operations suffer from two main limitations. First, they fail to handle many large datasets practically used in real applications. Second, they cannot handle arbitrary spatial lines that practically form polygons, e.g., city blocks, but they are given as a set of scattered lines. This work proposes a distributed and scalable way to compute the overlay operation and its related supported queries. Our operations also support arbitrary spatial lines through a scalable polygonization process. We address the issues of efficiently distributing the lines and overlay operators and offer various optimizations that improve performance. Our experiments demonstrate that the proposed scalable solution can efficiently compute the overlay of large real datasets. 

Within the dynamic world of Big Data, traditional systems typically operate in a passive mode, processing and responding to user queries by returning the requested data. However, this methodology falls short of meeting the evolving demands of users who not only wish to analyze data but also to receive proactive updates on topics of interest. To bridge this gap, Big Active Data (BAD) frameworks have been proposed to support extensive data subscriptions and analytics for millions of subscribers. As data volumes and the number of interested users continue to increase, it is imperative to optimize BAD systems for enhanced scalability, performance, and efficiency. To this end, this paper introduces three main optimizations, namely: strategic aggregation, intelligent modifications to the query plan, and early result filtering, all aimed at reinforcing a BAD platform’s capability to actively manage and efficiently process soaring rates of incoming data and distribute notifications to larger numbers of subscribers.