Irregularly sampled time series data with missing values is a observed in many fields like healthcare, astronomy, and climate science. Interpolation of these types of time series is crucial for tasks such as root cause analysis and medical diagnosis, as well as for smoothing out irregular or noisy data. To address this challenge, we present a novel encoder-decoder architecture called “Tripletformer” for probabilistic interpolation of irregularly sampled time series with missing values. This attention-based model operates on sets of observations, where each element is composed of a triple of time, channel, and value. The encoder and decoder of the Tripletformer are designed with attention layers and fully connected layers, enabling the model to effectively process the presented set elements. We evaluate the Tripletformer against a range of baselines on multiple real-world and synthetic datasets and show that it produces more accurate and certain interpolations. Results indicate an improvement in negative loglikelihood error by up to 32% on real-world datasets and 85% on synthetic datasets when using the Tripletformer compared to the next best model.

Asynchronous Time Series is a multivariate time series where all the channels are observed asynchronously-independently, making the time series extremely sparse when aligning them. We often observe this effect in applications with complex observation processes, such as health care, climate science, and astronomy, to name a few. Because of the asynchronous nature, they pose a significant challenge to deep learning architectures, which presume that the time series presented to them are regularly sampled, fully observed, and aligned with respect to time. This paper proposes a novel framework, that we call Deep Convolutional Set Functions (DCSF), which is highly scalable and memory efficient, for the asynchronous time series classification task. With the recent advancements in deep set learning architectures, we introduce a model that is invariant to the order in which time series’ channels are presented to it. We explore convolutional neural networks, which are well researched for the closely related problem-classification of regularly sampled and fully observed time series, for encoding the set elements. We evaluate DCSF for AsTS classification, and online (per time point) AsTS classification. Our extensive experiments on multiple real world and synthetic datasets verify that the suggested model performs substantially better than a range of state-of-the-art models in terms of accuracy and run time. We increase the accuracy of the mini-Physionet dataset upto 2%; real datasets with synthetic setups of both AsTS, and TSMV upto 30%.

We propose a generalized framework for influence maximization in large-scale, time evolving networks. Many real-life influence graphs such as social networks, telephone networks, and IP traffic data exhibit dynamic characteristics, e.g., the underlying structure and communication patterns evolve with time. Correspondingly, we develop a dynamic framework for the influence maximization problem, where we perform effective local updates to quickly adjust the top-k influencers, as the structure and communication patterns in the network change. We design a novel N-Family method (N=1, 2, 3, …) based on the maximum influence arborescence (MIA) propagation model with approximation guarantee of (1 − 1/e). We then develop heuristic algorithms by extending the N-Family approach to other information propagation models (e.g., independent cascade) and influence maximization algorithms (e.g., CELF, reverse reachable sketch). Based on a detailed empirical analysis over several real-world, dynamic, and large-scale networks, we find that our proposed solution, N-Family improves the updating time of the top-k influencers by 1 ∼ 2 orders of magnitude, compared to existing algorithms, while ensuring similar memory usage and influence spreads.

This paper demonstrates PERC --- our system for crowdsourced entity resolution with human errors. Entity Resolution (ER) is a critical step in data cleaning and analytics. Although many machine-based methods existed for ER task, crowdsourcing is becoming increasingly important since humans can provide more insightful information for complex tasks, e.g., clustering of images and natural language processing. However, human workers still make mistakes due to lack of domain expertise or seriousness, ambiguity, or even malicious intent. To this end, we present a system, called PERC (probabilistic entity resolution with crowd errors), which adopts an uncertain graph model to address the entity resolution problem with noisy crowd answers. Using our framework, the problem of ER becomes equivalent to finding the maximum-likelihood clustering. In particular, we propose a novel metric called "reliability" to measure the quality of a clustering, which takes into account both the connected-ness inside and across all clusters. PERC then automatically selects the next question to ask the crowd that maximally increases the "reliability" of the current clustering. This demonstration highlights (1) a reliability-based next crowd-sourcing framework for crowdsourced ER, which does not require any user-defined threshold, and no apriori information about the error rate of the crowd workers, (2) it improves the ER quality by 15% and reduces the crowdsourcing cost by 50% compared to state-of-the-art methods, and (3) its GUI can interact with users to help them compare different crowdsourced ER algorithms, their intermediate ER results as they progress, and their selected next crowdsourcing questions in a user-friendly manner. Our demonstration video is at: https://www.youtube.com/watch?v=rQ7nu3b8zXY.

Crowdsourcing is becoming increasingly important in entity resolution tasks due to their inherent complexity such as clustering of images and natural language processing. Humans can provide more insightful information for these difficult problems compared to machine-based automatic techniques. Nevertheless, human workers can make mistakes due to lack of domain expertise or seriousness, ambiguity, or even due to malicious intents. The bulk of literature usually deals with human errors via majority voting or by assigning a universal error rate over crowd workers. However, such approaches are incomplete, and often inconsistent, because the expertise of crowd workers are diverse with possible biases, thereby making it largely inappropriate to assume a universal error rate for all workers over all crowdsourcing tasks. We mitigate the above challenges by considering an uncertain graph model, where the edge probability between two records A and B denotes the ratio of crowd workers who voted YES on the question if A and B are same entity. To reflect independence across different crowdsourcing tasks, we apply the notion of possible worlds, and develop parameter-free algorithms for both next crowdsourcing and entity resolution tasks. In particular, for next crowdsourcing, we identify the record pair that maximally increases the reliability of the current clustering. Since reliability takes into account the connected-ness inside and across all clusters, this metric is more effective in deciding next questions, in comparison with state-of-the-art works, which consider local features, such as individual edges, paths, or nodes to select next crowdsourcing questions. Based on detailed empirical analysis over real-world datasets, we find that our proposed solution, PERC (probabilistic entity resolution with imperfect crowd) improves the quality by 15% and reduces the overall cost by 50% for the crowdsourcing-based entity resolution.