Nan Tang

Qatar Foundation · QCRI

Knowledge bases (KBs), which store high-quality information, are crucial for many applications, such as enhancing search results and serving as external sources for data cleaning. Not surprisingly, there exist outdated facts in most KBs due to the rapid change of information. Naturally, it is important to keep KBs up-to-date. Traditional wisdom has...

Successful machine learning (ML) needs to learn from good data. However, one common issue about train data for ML practitioners is the lack of good features. To mitigate this problem, feature augmentation is often employed by joining with (or enriching features from) multiple tables, so as to become feature-rich ML. A consequent problem is that the...

Fact verification has attracted a lot of research attention recently, e.g., in journalism, marketing, and policymaking, as misinformation and disinformation online can sway one's opinion and affect one's actions. While fact-checking is a hard task in general, in many cases, false statements can be easily debunked based on analytics over tables with...

Entity resolution (ER) is a core data integration problem that identifies pairs of data instances referring to the same real-world entities, and the state-of-the-art results of ER are achieved by deep learning (DL) based approaches. However, DL-based approaches typically require a large amount of labeled training data (i.e. , matching and non-match...

Data exploration—the problem of extracting knowledge from database even if we do not know exactly what we are looking for —is important for data discovery and analysis. However, precisely specifying SQL queries is not always practical, such as “finding and ranking off-road cars based on a combination of Price, Make, Model, Age, Mileage, etc”—not on...

The lack of sufficient labeled data is a key bottleneck for practitioners in many real-world supervised machine learning (ML) tasks. In this paper, we study a new problem, namely selective data acquisition in the wild for model charging : given a supervised ML task and data in the wild (e.g., enterprise data warehouses, online data repositories, da...

Supporting the translation from natural language (NL) query to visualization (NL2VIS) can simplify the creation of data visualizations because if successful, anyone can generate visualizations by their natural language from the tabular data. The state-of-the-art NL2VIS approaches ( e.g. , NL4DV and FlowSense) are based on semantic parsers and heur...

Entity categorization, the process of categorizing entities into groups, is an important problem with many applications. However, in practice, many entities are mis-categorized, such as Google Scholar and Amazon products. In this paper, we study the problem of discovering mis-categorized entities from a given group of categorized entities. This pro...

Entity matching (EM) finds data instances that refer to the same real-world entity. Most EM solutions perform blocking then matching. Many works have applied deep learning (DL) to matching, but far fewer works have applied DL to blocking. These blocking works are also limited in that they consider only a simple form of DL and some of them require l...

Deep learning (DL) has widespread applications and has revolutionized many industries. Although automated machine learning (AutoML) can help us away from coding for DL models, the acquisition of lots of high-quality data for model training remains a main bottleneck for many DL projects, simply because it requires high human cost. Despite many works...

Patterns (or regex-based expressions) are widely used to constrain the format of a domain (or a column), e.g. , a Year column should contain only four digits, and thus a value like "1980-" might be a typo. Moreover, integrity constraints (ICs) defined over multiple columns, such as (conditional) functional dependencies and denial constraints, e.g....

Spatio-temporal data analysis is very important in many time-critical applications. We take Coronavirus disease (COVID-19) as an example, and the key questions that everyone will ask every day are: how does Coronavirus spread? where are the high-risk areas? where have confirmed cases around me? Interactive data analytics, which allows general users...

Data pipelines are the new code. Consequently, data scientists need new tools to support the often time-consuming process of debugging their pipelines. We introduce Dagger , an end-to-end system to debug and mitigate data-centric errors in data pipelines, such as a data transformation gone wrong or a classifier underperforming due to noisy training...

Data visualization is crucial in data-driven decision making. However, bad visualizations generated from dirty data often mislead the users to understand the data and to draw wrong decisions. We present VisClean, a system that can progressively visualize data with improved quality through interactive and visualization-aware data cleaning. We will d...

In this work, we present a self-driving data visualization system, called DeepEye , that automatically generates and recommends visualizations based on the idea of visualization by examples. We propose effective visualization recognition techniques to decide which visualizations are meaningful and visualization ranking techniques to rank the go...

Data visualization is crucial in today’s data-driven business world, which has been widely used for helping decision making that is closely related to major revenues of many industrial companies. However, due to the high demand of data processing w.r.t. the volume, velocity, and veracity of data, there is an emerging need for database experts to he...

Many data problems are solved when the right view of a combination of datasets is identified. Finding such a view is challenging because of the many tables spread across many databases, data lakes, and cloud storage in modern organizations. Finding relevant tables, and identifying how to combine them is a difficult and time-consuming process that h...

Data scientists spend over 80% of their time (1) parameter-tuning machine learning models and (2) iterating between data cleaning and machine learning model execution. While there are existing efforts to support the first requirement, there is currently no integrated workflow system that couples data cleaning and machine learning development. The p...

Entity resolution (ER) seeks to identify the set of tuples in a dataset that refer to the same real-world entity. It is one of the fundamental and well studied problems in data integration with applications in diverse domains such as banking, insurance, e-commerce, and so on. Machine Learning and Deep Learning based methods provide the state-of-the...

An end-to-end data integration system requires human feedback in several phases, including collecting training data for entity matching, debugging the resulting clusters, confirming transformations applied on these clusters for data standardization, and finally, reducing each cluster to a single, canonical representation (or "golden record"). The t...

Detecting erroneous values is a key step in data cleaning. Error detection algorithms usually require a user to provide input configurations in the form of rules or statistical parameters. However, providing a complete, yet correct, set of configurations for each new dataset is not trivial, as the user has to know about both the dataset and the err...

Knowledge discovery is critical to successful data analytics. We propose a new type of meta-knowledge, namely pattern functional dependencies (PFDs), that combine patterns (or regex-like rules) and integrity constraints (ICs) to model the dependencies (or meta-knowledge) between partial values (or patterns) across different attributes in a table. P...

Optimizing the physical data storage and retrieval of data are two key database management problems. In this paper, we propose a language that can express a wide range of physical database layouts, going well beyond the row- and column- based methods that are widely used in database management systems. We also build a compiler for this language, wh...

2019 Association for Computing Machinery. Detecting erroneous values is a key step in data cleaning. Error detection algorithms usually require a user to provide input configurations in the form of rules or statistical parameters. However, providing a complete, yet correct, set of configurations for each new dataset is not trivial, as the user has...

Entity resolution (ER) is one of the fundamental problems in data integration, where machine learning (ML) based classifiers often provide the state-of-the-art results. Considerable human effort goes into feature engineering and training data creation. In this paper, we investigate a new problem: Given a dataset D_T for ER with limited or no traini...

Missing values are common in real-world data and may seriously affect data analytics such as simple statistics and hypothesis testing. Generally speaking, there are two types of missing values: explicitly missing values (i.e., NULL values), and implicitly missing values (a.k.a. disguised missing values (DMVs)) such as “11111111" for a phone number...

Given a relational table, we study the problem of detecting and repairing erroneous data, as well as marking correct data, using well curated knowledge bases (KBs). We propose detective rules (DRs), a new type of data cleaning rules that can make actionable decisions on relational data, by building connections between a relation and a KB. The main...

Despite the efforts in 70+ years in all aspects of entity resolution (ER), there is still a high demand for democratizing ER - by reducing the heavy human involvement in labeling data, performing feature engineering, tuning parameters, and defining blocking functions. With the recent advances in deep learning, in particular distributed representati...

Solving business problems increasingly requires going beyond the limits of a single data processing platform (platform for short), such as Hadoop or a DBMS. As a result, organizations typically perform tedious and costly tasks to juggle their code and data across different platforms. Addressing this pain and achieving automatic cross-platform data...

Despite the efforts in 70+ years in all aspects of entity resolution (ER), there is still a high demand for democratizing ER - by reducing the heavy human involvement in labeling data, performing feature engineering, tuning parameters, and defining blocking functions. With the recent advances in deep learning, in particular distributed representati...

Creating good visualizations for ordinary users is hard, even with the help of the state-of-the-art interactive data visualization tools, such as Tableau, Qlik, because they require the users to understand the data and visualizations very well. DeepEye is an innovative visualization system that aims at helping everyone create good visualizations si...

In order for an enterprise to gain insight into its internal business and the changing outside environment, it is essential to provide the relevant data for in-depth analysis. Enterprise data is usually scattered across departments and geographic regions, and is often inconsistent. Data scientists spend the majority of their time finding, preparing...

Employees that spend more time finding relevant data than analyzing it suffer a data discovery problem. The large volume of data in enterprises, and sometimes the lack of knowledge of the schemas aggravates this problem. Similar to how we navigate the Web today, we propose to identify semantic links that assist analysts in their discovery tasks. Th...

It is well established that missing values, if not dealt with properly, may lead to poor data analytics models, misleading conclusions, and limitation in the generalization of findings. A key challenge in detecting these missing values is when they manifest themselves in a form that is otherwise valid, making it hard to distinguish them from other...

2018 IEEE. Employees that spend more time finding relevant data than analyzing it suffer from a data discovery problem. The large volume of data in enterprises, and sometimes the lack of knowledge of the schemas aggravates this problem. Similar to how we navigate the Web, we propose to identify semantic links that assist analysts in their discovery...

2018 IEEE. In order for an enterprise to gain insight into its internal business and the changing outside environment, it is essential to provide the relevant data for in-depth analysis. Enterprise data is usually scattered across departments and geographic regions and is often inconsistent. Data scientists spend the majority of their time finding,...

Past. Data curation - the process of discovering, integrating, and cleaning data - is one of the oldest data management problems. Unfortunately, it is still the most time consuming and least enjoyable work of data scientists. So far, successful data curation stories are mainly ad-hoc solutions that are either domain-specific (for example, ETL rules...

Data visualization transforms data into images to aid the understanding of data; therefore, it is an invaluable tool for explaining the significance of data to visually inclined people. Given a (big) dataset, the essential task of visualization is to visualize the data to tell compelling stories by selecting, filtering, and transforming the data, a...

Entity Resolution (ER) is a fundamental problem with many applications. Machine learning (ML)-based and rule-based approaches have been widely studied for decades, with many efforts being geared towards which features/attributes to select, which similarity functions to employ, and which blocking function to use - complicating the deployment of an E...

Entity matching (EM) is a critical part of data integration. We study how to synthesize entity matching rules from positive-negative matching examples. The core of our solution is program synthesis, a powerful tool to automatically generate rules (or programs) that satisfy a given high-level specification, via a predefined grammar. This grammar des...

Four key subprocesses in data integration are: data preparation (i.e., transforming and cleaning data), schema integration (i.e., lining up like attributes), entity resolution (i.e., finding clusters of records that represent the same entity) and entity consolidation (i.e., merging each cluster into a "golden record" which contains the canonical va...

Finding relevant data for a specific task from the numerous data sources available in any organization is a daunting task. This is not only because of the number of possible data sources where the data of interest resides, but also due to the data being scattered all over the enterprise and being typically dirty and inconsistent. In practice, data...

Error detection is the process of identifying problematic data cells that are different from their ground truth. Functional dependencies (FDs) have been widely studied in support of this process. Oftentimes, it is assumed that FDs are given by experts. Unfortunately, it is usually hard and expensive for the experts to define such FDs. In addition,...

Entity matching (EM) is a critical part of data integration and cleaning. In many applications, the users need to understand why two entities are considered a match, which reveals the need for interpretable and concise EM rules. We model EM rules in the form of General Boolean Formulas (GBFs) that allows arbitrary attribute matching combined by con...

Finding relevant data for a specific task from the numerous data sources available in any organization is a daunting task. This is not only because of the number of possible data sources where the data of interest resides, but also due to the data being scattered all over the enterprise and being typically dirty and inconsistent. In practice, data...

2017 ACM. Entity matching (EM) is a critical part of data integration and cleaning. In many applications, the users need to understand why two entities are considered a match, which reveals the need for interpretable and concise EM rules. We model EM rules in the form of General Boolean Formulas (GBFs) that allows arbitrary attribute matching combi...

Inequality joins, which is to join relations with inequality conditions, are used in various applications. Optimizing joins has been the subject of intensive research ranging from efficient join algorithms such as sort-merge join, to the use of efficient indices such as $$B^+$$ B + -tree, $$R^*$$ R ∗ -tree and Bitmap. However, inequality joins have...

Integrity constraint based data repairing is an iterative process consisting of two parts: detect and group errors that violate given integrity constraints (ICs); and modify values inside each group such that the modified database satisfies those ICs. However, most existing automatic solutions treat the process of detecting and grouping errors stra...

Data cleaning has played a critical role in ensuring data quality for enterprise applications. Naturally, there has been extensive research in this area, and many data cleaning algorithms have been translated into tools to detect and to possibly repair certain classes of errors such as outliers, duplicates, missing values, and violations of integri...

We present Falcon, an interactive, deterministic, and declarative data cleaning system, which uses SQL update queries as the language to repair data. Falcon does not rely on the existence of a set of pre-defined data quality rules. On the contrary, it encourages users to explore the data, identify possible problems, and make updates to fix them. Bo...

Many emerging applications, from domains such as healthcare and oil & gas, require several data processing systems for complex analytics. This demo paper showcases system, a framework that provides multi-platform task execution for such applications. It features a three-layer data processing abstraction and a new query optimization approach for mul...

Inequality joins, which join relational tables on inequality conditions, are used in various applications. While there have been a wide range of optimization methods for joins in database systems, from algorithms such as sort-merge join and band join, to various indices such as B+-tree, R∗-tree and Bitmap, inequality joins have received little atte...

Data analytics is at the core of any organization that wants to obtain measurable value from its growing data assets. Data analytic tasks may range from simple to extremely complex pipelines, such as data extraction, transformation and loading, online analytical processing, graph processing, and machine learning (ML). Following the dictum “one size...

Classical approaches to clean data have relied on using integrity constraints, statistics, or machine learning. These approaches are known to be limited in the cleaning accuracy, which can usually be improved by consulting master data and involving experts to resolve ambiguity. The advent of knowledge bases KBs both general-purpose and within enter...

Data cleansing approaches have usually focused on detecting and fixing errors with little attention to scaling to big datasets. This presents a serious impediment since data cleansing often involves costly computations such as enumerating pairs of tuples, handling inequality joins, and dealing with user-defined functions. In this paper, we present...

One notoriously hard data cleaning problem is, given a database, how to precisely capture which value is correct (i.e., proof positive) or wrong (i.e., proof negative). Although integrity constraints have been widely studied to capture data errors as violations, the accuracy of data cleaning using integrity constraints has long been controversial....

Data cleaning with guaranteed reliability is hard to achieve without accessing external sources, since the truth is not necessarily discoverable from the data at hand. Furthermore, even in the presence of external sources, mainly knowledge bases and humans, effectively leveraging them still faces many challenges, such as aligning heterogeneous data...

Data cleaning is, in fact, a lively subject that has played an important part in the history of data management and data analytics, and it still is undergoing rapid development. Moreover, data cleaning is considered as a main challenge in the era of big data, due to the increasing volume, velocity and variety of data in many applications. This pape...

This article introduces a new approach for conflict resolution: given a set of tuples pertaining to the same entity, it identifies a single tuple in which each attribute has the latest and consistent value in the set. This problem is important in data integration, data cleaning, and query answering. It is, however, challenging since in practice, re...

Entity resolution (ER), the process of identifying and eventually merging records that refer to the same real-world entities, is an important and long-standing problem. We present Nadeef/Er, a generic and interactive entity resolution system, which is built as an extension over our open-source generalized data cleaning system Nadeef. Nadeef/Er prov...

We present NADEEF, an extensible, generic and easy-to-deploy data cleaning system. NADEEF distinguishes between a programming interface and a core to achieve generality and extensibility. The programming interface allows users to specify data quality rules by writing code that implements predefined classes. These classes uniformly define what is wr...

Despite the increasing importance of data quality and the rich theoretical and practical contributions in all aspects of data cleaning, there is no single end-to-end off-the-shelf solution to (semi-)automate the detection and the repairing of violations w.r.t. a set of heterogeneous and ad-hoc quality constraints. In short, there is no commodity pl...