Early Anomaly Detection (AD) in sensor-based Multivariate Time Series (MTS) is crucial for addressing signs of operational failures. However, existing AD methods either struggle to identify anomalies at an early stage or lean heavily on intricate neural networks and extensive data for model training, compromising clarity and interpretability. To bridge this gap, we pioneered CAD, a novel AD framework based on correlation analysis. It harnesses Time-Series Graphs (TSGs) to monitor sensor correlation changes. By meticulously analyzing these changes, CAD excels in ascertaining the precise time of anomalies and identifying the implicated sensors. In this demonstration, we introduce EADS, an Early Anomaly Detection System built upon CAD for sensor-based MTS. We navigate multiple scenarios to illustrate the prowess of EADS in serving as an early AD benchmark platform, offering insightful abnormal time interpretability, and facilitating timely predictive maintenance. The source code is available at https://github.com/YihaoAng/EADS/.

Machine learning models are only as good as their training data. Simple models trained on well-chosen features extracted from the raw data often outperform complex models trained directly on the raw data. Data preparation pipelines, which clean and derive features from the data, are therefore important for machine learning applications. However, constructing such pipelines is a resource-intensive process that involves deep human expertise. Our goal is to design an efficient framework for automatically finding high-quality data preparation pipelines. The main challenge is how to explore a large search space of pipeline components with the objective of computing features that maximize the performance of the downstream models. Existing solutions are limited in terms of feature quality, which results in low accuracies of the downstream models, while incurring significant runtime overhead. We present CtxPipe, a novel framework that addresses the limitations of previous works by leveraging contextual information to improve the pipeline construction process. Specifically, it uses pre-trained embedding models to capture the data semantics, which are then used to guide the selection of pipeline components. We implement CtxPipe with deep reinforcement learning and evaluate it against state-of-the-art automated pipeline construction solutions. Our comprehensive experiments demonstrate that CtxPipe outperforms all of the baselines in both model performance and runtime cost.

Time Series Generation (TSG) is essential in many industries for generating synthetic data that mirrors real-world characteristics. TSGBench has advanced the field by offering comprehensive evaluations and unique insights for selecting suitable TSG methods. However, translating these advancements to industry applications is hindered by a cognitive gap among professionals and the absence of a dynamic platform for method comparison and evaluation. To address these issues, we introduce TSGAssist, an interactive assistant that integrates the strengths of TSGBench and harnesses Large Language Models (LLMs) and Retrieval-Augmented Generation (RAG) for TSG recommendations and benchmarking. Our demonstration highlights its effectiveness in (1) enhancing TSG understanding, (2) providing industry-specific recommendations, and (3) offering a comprehensive benchmarking platform, illustrating its potential to ease industry professionals' navigation through the TSG landscape and encourage broader application across industries.

Early detection of anomalies from sensor-based Multivariate Time Series (MTS) is vital for timely response to the signs of operation failures and errors. While many interesting works have been done toward solving this problem, existing methods typically detect such anomalies as outliers by making certain assumptions that allow efficient and easily understandable solutions to be used but might not be applicable to time series. Meanwhile, unsupervised deep learning-based methods might be highly accurate but often lead to challenges for real-time industrial scenarios, e.g., requiring a large amount of training data and producing unstable output.In this paper, we propose a new approach, CAD, to detect anomalies from sensor-based MTS. We aim to leverage the latent correlations between sensors by first converting the MTS into a sequence of Time-Series Graphs (TSGs) that connect sensors to their highly correlated neighbors within a certain time period. Then, we track the unusual correlation variations between sensors on the sequence of TSGs. By analyzing the correlation variations with a theoretical guarantee, CAD can detect the time of occurrence for the anomalies simultaneously with the sensors that are affected as early as possible.Extensive experiments over eight real-world datasets show that CAD is effective, scalable, yet stable compared to nine state-of-the-art methods while keeping comparable efficiency. Moreover, it maintains above 85% accuracy on large-scale datasets with over 1,000 sensors. Notably, CAD can determine relevant sensors in a very early stage of the anomaly so that timely predictive maintenance can be done. The code is available at https://github.com/YihaoAng/CAD.

Synthetic Time Series Generation (TSG) is crucial in a range of applications, including data augmentation, anomaly detection, and privacy preservation. Although significant strides have been made in this field, existing methods exhibit three key limitations: (1) They often benchmark against similar model types, constraining a holistic view of performance capabilities. (2) The use of specialized synthetic and private datasets introduces biases and hampers generalizability. (3) Ambiguous evaluation measures, often tied to custom networks or downstream tasks, hinder consistent and fair comparison. To overcome these limitations, we introduce TSGBench, the inaugural Time Series Generation Benchmark, designed for a unified and comprehensive assessment of TSG methods. It comprises three modules: (1) a curated collection of publicly available, real-world datasets tailored for TSG, together with a standardized preprocessing pipeline; (2) a comprehensive evaluation measures suite including vanilla measures, new distance-based assessments, and visualization tools; (3) a pioneering generalization test rooted in Domain Adaptation (DA), compatible with all methods. We have conducted comprehensive experiments using TSGBench across a spectrum of ten real-world datasets from diverse domains, utilizing ten advanced TSG methods and twelve evaluation measures. The results highlight the reliability and efficacy of TSGBench in evaluating TSG methods. Crucially, TSGBench delivers a statistical analysis of the performance rankings of these methods, illuminating their varying performance across different datasets and measures and offering nuanced insights into the effectiveness of each method.

Modern data analytics pipelines are highly dynamic, as they are constantly monitored and fine-tuned by both data engineers and scientists. Recent systems managing pipelines ease creating, deploying, and tracking their evolution. However, privacy concerns emerge as many of them are deployed on the public cloud with less or no trust. Unfortunately, the unique nature of pipelines prevents the adoption of existing confidential computing techniques with different computational patterns and large performance overhead. Being a potential approach, trusted execution environments (TEEs) are efficient in protecting the confidentiality and integrity of data and computation. However, fast-changing pipelines with latency requirements bring the challenge of reducing the cold start overhead --- the main bottleneck in the latest TEE. To support end-to-end private pipeline evolution, we present SecCask, a TEE-based data analytics pipeline management system. SecCask overcomes the problems of a naive design that isolates complete pipeline execution in one enclave by administering enclaves and runtimes. To reduce cold start overheads, our approach consists of reusing trusted runtimes for different pipeline components and caching them to avoid the cost of initialization. We leverage the latest Intel SGX to conduct experiments on representative workloads. The results demonstrate that SecCask reduces the total execution time by 68.4% compared to not reusing, is faster than running all components in one enclave, and incurs a modest average performance overhead of 29.9% over insecure baselines.

In this work, we present our implementation for managing moving objects on top of a popular relational database system MySQL, namely SpADE (spatio-temporal autonomic database engine for managing moving objects). In our SpADE system, non-static entities like vehicles and pedestrians are abstracted as moving objects. They obtain positioning information with GPS (Global Positioning System) receivers installed, and are able to communicate via wireless network with the server, sending queries to and receiving results from it. The server is responsible for managing moving object information and processing queries from mobile users. By employing the industry standard JDBC for the data access, our server can also support providing services for other application interfaces such as the Web.

Skyline queries are well suited when retrieving data according to multiple criteria. While most previous work has assumed a centralized setting this paper considers skyline querying in a mobile and distributed setting, where each mobile device is capable of holding only a portion of the whole dataset; where devices communicate through mobile ad hoc networks; and where a query issued by a mobile user is interested only in the user’s local area, although a query generally involves data stored on many mobile devices due to the storage limitations. We present techniques that aim to reduce the costs of communication among mobile devices and reduce the execution time on each single mobile device. For the former, skyline query requests are forwarded among mobile devices in a deliberate way, such that the amount of data to be transferred is reduced. For the latter, specific optimization measures are proposed for resource-constrained mobile devices. We conduct extensive experiments to show that our proposal performs efficiently in real mobile devices and simulated wireless ad hoc networks.

The literature on skyline algorithms has so far dealt mainly with queries of static query points over static data sets. With the increasing number of mobile service applications and users, however, the need for continuous skyline query processing has become more pressing. A continuous skyline query involves not only static dimensions, but also the dynamic one. In this paper, we examine the spatiotemporal coherence of the problem and propose a continuous skyline query processing strategy for moving query points. First, we distinguish the data points that are permanently in the skyline and use them to derive a search bound. Second, we investigate the connection between the spatial positions of data points and their dominance relationship, which provides an indication of where to find changes in the skyline and how to maintain the skyline continuously. Based on the analysis, we propose a kinetic-based data structure and an efficient skyline query processing algorithm. We concisely analyze the space and time costs of the proposed method and conduct an extensive experiment to evaluate the method. To the best of our knowledge, this is the first work on continuous skyline query processing

No abstract available.

In this paper, we present a novel structure called the hierarchical degree-of-visibility tree (HDoV-tree) for visibility query processing in visualization systems. The HDoV-tree builds on and extends the R-tree such that 1) the search space is pruned based on the degree of visibility of objects and 2) internal nodes store level-of-details (LoDs) that represent a collection of objects in a coarser form. We propose two tree traversal algorithms that balance performance and visual fidelity, explore three storage structures for the HDoV-tree, and develop novel caching techniques for disk-based HDoV-tree. We implemented the HDoV-tree in a prototype walkthrough system called VISUAL. Our experimental study shows that VISUAL can lead to high frame rates without compromising visual fidelity.

In a visualization system, one of the key issues is to optimize performance and visual fidelity. This is especially critical for large virtual environments where the models do not fit into the memory. Here, we present a novel structure called HDoV-tree that can be tuned to provide excellent visual fidelity and performance based on the degree of visibility of objects. HDoV-tree also exploits internal level-of-details (LoDs) that represent a collection of objects in a coarser form. We also propose three storage structures for the HDoV-tree. We implemented HDoV-tree in a prototype walkthrough system called VISUAL. We have evaluated the HDoV-tree on visibility queries, and also compared the performance of VISUAL against REVIEW, a walkthrough system based on R-tree. Our results show that the HDoV-tree is an efficient structure. Moreover, VISUAL can lead to high frame rates without compromising visual fidelity.

No abstract available.