Abstract The empirical variance estimation and its corresponding top- k query is a fundamental problem in the data mining and data analytics and serves as an inherent building block for many clustering and feature selection algorithms. Since the exact computation requires scanning the whole dataset which will be prohibitively expensive for many real-time applications, all existing studies in the literature are dedicated to find the approximate solutions by using the sampling techniques. For the top- k query processing, we observe that all existing studies analyze the error of the estimated variance of each selected attribute independently by using the traditional centrality inequality (e.g., Chernoff bounds/Hoeffding’s inequality) and then adopt the traditional union bound to estimate the aggregate error of the k selected attributes. As such, the bound is significantly loose and renders their algorithm sensitive to the parameter k . Motivated by this, in this paper, we propose a once-for-all progressive sampling algorithm, namely Top- k E mpirical V ariance Computation with Rademacher A verage (EVA) , for jointly analyzing the aggregate error of the variances of all attributes one-for-all. In our algorithm, the tuples are sampled iteratively in batches. In each iteration, we estimate the accuracy currently achieved with the tuples already being sampled and derive the error bound by adopting a key concept called Rademacher Average from the statistical machine learning theory. Our error estimation algorithm enjoys two features. Firstly, it is data-dependent which fully makes use of the tuples already sampled and help us terminate the algorithm earlier once our desired accuracy is achieved. Secondly and more importantly, it estimates the aggregate error of the selected attributes simultaneously once-for-all which considers their inter-relation and as such, it is tighter than the traditional union bound-based method. Our empirical study shows that our algorithm outperforms the state-of-the-art algorithms by orders of magnitudes in terms of the efficiency with the same accuracy guarantee.

The interactive regret query is one of the most representative multi-criteria decision-making queries. It identifies tuples that satisfy users' preferences via iterative user interaction. In each interactive round, it asks users a question to learn about their preferences. Once the users' preferences are sufficiently learned, it returns tuples based on the learned preferences. Nevertheless, existing algorithms for this query are typically short-term focused, i.e., they ask questions by only considering each individual interactive round, without taking the overall interaction process as a whole. This may harm the long-term benefit, leading to a large number of rounds in the overall process. To address this, we propose two algorithms based on reinforcement learning, aiming to effectively improve the overall interaction process. We first formalize the interactive regret query as a Markov Decision Process. Then, we propose two interactive algorithms, namely EA and AA, which utilize reinforcement learning to learn a good policy for selecting questions during the interaction. Both algorithms are optimized not only for the current interactive round but also for the overall interaction process, with the goal of minimizing the total number of questions asked (i.e., the total number of interactive rounds). Extensive experiments were conducted on synthetic and real datasets, showing that our algorithms reduce the number of questions asked by approximately 50% compared to existing ones under typical settings.

Natural Language Interfaces (NLIs) have transformed data interaction by enabling natural language querying and visualization of tabular data. Despite the growing importance of NLIs, prior research has examined querying and visualization tasks separately, lacking a unified perspective, especially in the era of Large Language Models (LLMs). To fill this gap, this survey provides a comprehensive analysis of NLIs for tabular data, examining their evolution and fundamental components: datasets, evaluation metrics, and architectural designs. By analyzing over 60 approaches and 38 datasets, we explore recent advancements in Text-to-SQL and Text-to-Vis tasks, focusing on semantic parsing techniques for natural language translation to SQL queries and visualization specifications. We evaluate the impact of LLMs on these systems, discussing their capabilities and limitations. Our systematic review serves as a roadmap for developing NLIs in the foundation model era.

BERT-like models have been widely adopted in text mining and web search due to their high accuracy. However, large BERT-like models suffer from inefficient online inference on GPUs for two main reasons. First, their high accuracy relies on large model depth, which linearly increases sequential computation on GPUs. Second, stochastic and dynamic online workloads lead to extra costs due to batching and padding. To address the problem, we present Student Parallelism for efficient GPU inference of BERT-like models under real-world online workloads. At its core, Student Parallelism adopts stacking distillation and boosting ensemble, distilling the original deep model into a group of shallow but virtually stacked student models running in parallel. This enables Student Parallelism to achieve a low model depth (e.g., two layers), and thus low inference latency while maintaining accuracy. In addition, we design adaptive student pruning to adjust the number of students according to the dynamic online workloads. For example, during workload bursts, it can temporarily decrease the number of students with minimal accuracy loss to improve system throughput. Extensive experiments on real-world datasets and workloads show that Student Parallelism achieves up to 4.1× lower latency while maintaining accuracy and up to 22.27× higher throughput during workload bursts.

The Single-Source Personalized PageRank (SSPPR) problem is widely used in information retrieval and recommendation systems. Traditional algorithms assume full knowledge of the network, making them inapplicable to online social networks (OSNs), where the topology is unknown, and users can only explore the network step by step via APIs. The only feasible approach for SSPPR in OSNs is Monte Carlo (MC) simulation, but traditional MC methods rely on static sampling, which lacks flexibility, delays feedback, and overestimates the number of required random walks. To address these limitations, we propose PANDA (Single-Source Personalized PageRank on OSNs with Rademacher Average), a progressive sampling algorithm. PANDA iteratively samples random walks in batches, estimating accuracy dynamically using Rademacher Average from statistical learning theory. This data-dependent approach allows for early termination once the desired accuracy is met. Additionally, PANDA features a dynamic sampling schedule to optimize efficiency. Empirical studies show that PANDA significantly outperforms existing methods, achieving the same accuracy with far greater efficiency.

With the advance of the geo-positioning technology, the terrain surface data has become increasingly popular and has drawn much research attention from both academia and industry. Answering a shortest-path query for a given source and a given destination on a terrain surface is a fundamental problem and has many applications including Geographical Information System and 3D virtual games. We observe that all existing exact algorithms are only aware of the position of the source point and is unaware of the information of the destination point. Motivated by this, in this paper, we propose an efficient algorithm, namelydirection-oriented algorithm (DIO Algorithm), for answering shortest-path queries on a terrain surface. The algorithm properly guides the search along a direction towards the destination instead of blindly searching all possible directions from the source point. To this end, we convert the geodesic shortest path problem to a shortest obstacle-free euclidean path problem in the 2D planar unfolding of the terrain surface. Based on this conversion, we derive for each part of the terrain surface a lower bound on the length of the shortest path from the source to the destination passing through the part with a novel method. The lower bounds provide useful information that can be used to decide the visiting order of the parts on the terrain surface and guides the search of finding the destination quickly. Our experiments verified that our algorithm runs faster than the state-of-the-art by more than one order of magnitude.

The emergence of natural language processing has revolutionized the way users interact with tabular data, enabling a shift from traditional query languages and manual plotting to more intuitive, language-based interfaces. The rise of large language models (LLMs) such as ChatGPT and its successors has further advanced this field, opening new avenues for natural language processing techniques. This survey presents a comprehensive overview of natural language interfaces for tabular data querying and visualization, which allow users to interact with data using natural language queries. We introduce the fundamental concepts and techniques underlying these interfaces with a particular emphasis on semantic parsing, the key technology facilitating the translation from natural language to SQL queries or data visualization commands. We then delve into the recent advancements in Text-to-SQL and Text-to-Vis problems from the perspectives of datasets, methodologies, metrics, and system designs. This includes a deep dive into the influence of LLMs, highlighting their strengths, limitations, and potential for future improvements. Through this survey, we aim to provide a roadmap for researchers and practitioners interested in developing and applying natural language interfaces for data interaction in the era of large language models.

Due to the advancement of geo-positioning technology, the terrain data has become increasingly popular and has drawn a lot of research effort from both academia and industry. The distance computation on the terrain surface is a fundamental and important problem that is widely applied in geographical information systems and 3D modeling. As could be observed from the existing studies, online computation of the distance on the terrain surface is very expensive. All existing index-based methods are only efficient under the case where the distance query must be performed among a small set of predefined points-of-interest known apriori. But, in general cases, they could not scale up to sizable datasets due to their intolerable oracle building time and space consumption. In this paper, we studied the arbitrary point-to-arbitrary point distance query on the terrain surface in which no assumption is imposed on the query points, and the distance query could be performed between any two arbitrary points. We propose an indexing structure, namely Efficient Arbitrary Point-to-Arbitrary Point Distance Oracle (EAR-Oracle), with theoretical guarantee on the accuracy, oracle building time, oracle size and query time. Our experiments demonstrate that our oracle enjoys excellent scalability and it scales up to enormous terrain surfaces but none of the existing index-based methods could be able to. Besides, it significantly outperforms all existing online computation methods by orders of magnitude in terms of the query time.

Image retrieval keeps attracting a lot of attention from both academic and industry over past years due to its variety of useful applications. Due to the rapid growth of deep learning approaches, more better feature vectors of images could be discovered for improving image retrieval. However, most (if not all) existing deep learning approaches consider the similarity between two images locally without considering the similarity among a group of similar images globally , and thus could not return accurate results. In this article, we study the image retrieval with manifold ranking (MR) which considers both the local similarity and the global similarity, which could give more accurate results. However, existing best-known algorithms have one of the following issues: (1) they require to build a bulky index, (2) some of them do not have any theoretical bound on the output, and (3) some of them are time-consuming. Motivated by this, we propose two algorithms, namely Monte Carlo-based MR ( MCMR ) and MCMR+ , for image retrieval, which do not have the above issues. We are the first one to propose an index-free manifold ranking image retrieval with the output theoretical bound. More importantly, our algorithms give the first best-known time complexity result of \(O(n \log n)\) where \(n\) is the total number of images in the database compared with the existing best-known result of \(O(n^2)\) in the literature of computing the exact top- \(k\) results with quality guarantee. Lastly, our experimental result shows that MCMR+ outperforms existing algorithms by up to four orders of magnitude in terms of query time.

Due to the advance of the geo-spatial positioning and the computer graphics technology, digital terrain data has become increasingly popular nowadays. Query processing on terrain data has attracted considerable attention from both the academic and the industry communities. Proximity queries such as the shortest path/distance query, k nearest/farthest neighbor query, and top- k closest/farthest pairs query are fundamental and important queries in the context of the terrain surfaces, and they have a lot of applications in Geographical Information System, 3D object feature vector construction, and 3D object data mining. In this article, we first study the most fundamental type of query, namely, shortest distance and path query, which is to find the shortest distance and path between two points of interest on the surface of the terrain. As observed by existing studies, computing the exact shortest distance/path is very expensive. Some existing studies proposed ϵ -approximate distance and path oracles, where ϵ is a non-negative real-valued error parameter. However, the best-known algorithm has a large oracle construction time, a large oracle size, and a large query time. Motivated by this, we propose a novel ϵ -approximate distance and path oracle called the S pace E fficient distance and path oracle (SE), which has a small oracle construction time, a small oracle size, and a small distance and path query time, thanks to its compactness of storing concise information about pairwise distances between any two points-of-interest. Then, we propose several algorithms for the k nearest/farthest neighbor and top- k closest/farthest pairs queries with the assistance of our distance and path oracle SE . Our experimental results show that the oracle construction time, the oracle size, and the distance and path query time of SE are up to two, three, and five orders of magnitude faster than the best-known algorithm, respectively. Besides, our algorithms for other proximity queries including k nearest/farthest neighbor queries and top- k closest/farthest pairs queries significantly outperform the state-of-the-art algorithms by up to two orders of magnitude.

Due to the prevalence of graph data, graph analysis is very important nowadays. One popular analysis on graph data is Random Walk with Restart (RWR) since it provides a good metric for measuring the proximity of two nodes in a graph. Although RWR is important, it is challenging to design an algorithm for RWR. To the best of our knowledge, there are no existing RWR algorithms which, at the same time, (1) are index-free, (2) return answers with a theoretical guarantee and (3) are efficient. Motivated by this, in this paper, we propose an index-free algorithm called Residue-Accumulated approach (ResAcc) which returns answers with a theoretical guarantee efficiently. Our experimental evaluations on large-scale real graphs show that ResAcc is up to 4 times faster than the best-known previous algorithm, guaranteeing the same accuracy. Under typical settings, the best-known algorithm ran around 1000 seconds on a large dataset containing 41.7 million nodes, which is too time-consuming, while ResAcc finished in 275 seconds with the same accuracy. Moreover, ResAcc is up to 6 orders of magnitude more accurate than the best-known algorithm in practice with the same execution time, which is considered as a substantial improvement.

Geo-textual data is ubiquitous nowadays, where each object has a location and is associated with some keywords. Many types of queries based on geo-textual data, termed as spatial keyword queries, have been proposed, and are to find optimal object(s) in terms of both its (their) location(s) and keywords. In this paper, we propose a new type of query called nearby-fit spatial keyword query (NSKQ), where an optimal object is defined based not only on the location and the keywords of the object itself, but also on those of the objects nearby. For example, in an application of finding a hotel, not only the location of a hotel but also the objects near the hotel (e.g., shopping malls, restaurants and bus stops nearby) might need to be taken into consideration.The query is proved to be NP-hard, and in order to perform the query efficiently, we developed two approximate algorithms with small constant approximation factors equal to 1.155 and 1.79. We conducted extensive experiments based on both real and synthetic datasets, which verified our algorithms.

Given two vertices of interest (POIs) s and t on a spatial network, a distance (path) query returns the shortest network distance (shortest path) from s to t. This query has a variety of applications in practice and is a fundamental operation for many database and data mining algorithms. In this paper, we propose an efficient distance and path oracle on dynamic road networks using the randomization technique. Our oracle has a good performance in practice and remarkably, and at the same time, it has a favorable theoretical bound. Specifically, it has O(n log2 n) (resp. O(n log2n)) preprocessing time (resp. space) and O(log4n log log n) (resp. O(log4n log log n+l)) distance query time (resp. shortest path query time) as well as O(log3n) update time with high probability (w.h.p.), where n is the number of vertices in the spatial network and l is the number of edges on the shortest path. Our experiments show that the existing oracles suffer from a huge updating time that renders them impractical and our oracle enjoys a negligible updating time and meanwhile has comparable query time and indexing cost with the best existing oracle.

Geo-textual data is ubiquitous nowadays, where each object has a location and is associated with some keywords. Many types of queries based on geo-textual data, termed as spatial keyword queries, have been proposed, and are to find optimal object(s) in terms of both its (their) location(s) and keywords. In this paper, we propose a new type of query called nearby-fit spatial keyword query (NSKQ), where an optimal object is defined based not only on the location and the keywords of the object itself, but also on those of the objects nearby. For example, in an application of finding a hotel, not only the location of a hotel but also the objects near the hotel (e.g., shopping malls, restaurants, and bus stops nearby) might need to be taken into consideration. The query is proved to be NP-hard, and in order to perform the query efficiently, we developed two approximate algorithms with small constant approximation factors equal to 1.155 and 1.79. We conducted extensive experiments based on both real and synthetic datasets, which verified our algorithms.

Image retrieval keeps attracting a lot of attention from both academic and industry over past years due to its variety of useful applications. Due to the rapid growth of deep learning approaches, more better feature vectors of images could be discovered for improving image retrieval. However, most (if not all) existing deep learning approaches consider the similarity between 2 images locally without considering the similarity among a group of similar images globally, and thus could not return accurate results. In this paper, we study the image retrieval with manifold ranking (MR) which considers both the local similarity and the global similarity, which could give more accurate results. However, existing best-known algorithms have one of the following issues: (1) They require a bulky index, (2) some of them do not have any theoretical bound on the output, and (3) some of them are time-consuming. Motivated by this, we propose an algorithm, namely Monte Carlo-based MR (MCMR) for image retrieval, which does not have the above issues. We are the first one to propose an index-free manifold ranking-based image retrieval with the output theoretical bound. Lastly, our experiments show that MCMR outperforms existing algorithms by up to 4 orders of magnitude in terms of query time.

In many commercial campaigns, we observe that there exists a tradeoff between the number of customers satisfied by the company and the profit gained. Merely satisfying as many customers as possible or maximizing the profit is not desirable. To this end, in this article, we propose a new problem called k - Satisfiability Assignment for Maximizing the Profit ( k -SAMP), where k is a user parameter and a non-negative integer. Given a set P of products and a set O of customers, k -SAMP is to find an assignment between P and O such that at least k customers are satisfied in the assignment and the profit incurred by this assignment is maximized. Although we find that this problem is closely related to two classic computer science problems, namely maximum weight matching and maximum matching, the techniques developed for these classic problems cannot be adapted to our k -SAMP problem. In this work, we design a novel algorithm called Adjust for the k -SAMP problem. Given an assignment A , Adjust iteratively increases the profit of A by adjusting some appropriate matches in A while keeping at least k customers satisfied in A . We prove that Adjust returns a global optimum. Extensive experiments were conducted that verified the efficiency of Adjust .

Due to the advance of the geo-spatial positioning and the computer graphics technology, digital terrain data become more and more popular nowadays. Query processing on terrain data has attracted considerable attention from both the academic community and the industry community. One fundamental and important query is the shortest distance query and many other applications such as proximity queries (including nearest neighbor queries and range queries), 3D object feature vector construction and 3D object data mining are built based on the result of the shortest distance query. In this paper, we study the shortest distance query which is to find the shortest distance between a point-of-interest and another point-of-interest on the surface of the terrain due to a variety of applications. As observed by existing studies, computing the exact shortest distance is very expensive. Some existing studies proposed ε-approximate distance oracles where ε is a non-negative real number and is an error parameter. However, the best-known algorithm has a large oracle construction time, a large oracle size and a large distance query time. Motivated by this, we propose a novel ε-approximate distance oracle called the Space Efficient distance oracle (SE) which has a small oracle construction time, a small oracle size and a small distance query time due to its compactness storing concise information about pairwise distances between any two points-of-interest. Our experimental results show that the oracle construction time, the oracle size and the distance query time of SE are up to two orders of magnitude, up to 3 orders of magnitude and up to 5 orders of magnitude faster than the best-known algorithm.