EDBT 2026 Demo / reviewers in the wild / expert
Lei Han 0003
dblp:75/2307-3
· DBLP profile ↗
19ranked-venue papers in the field
9as first author
12since 2021 · last 2025
0000-0002-7777-3592ORCID · verified
Domains — venue-derived; a paper can count in several
Information Retrieval & Web Search · 13 (5 first)Data Mining & Knowledge Discovery · 3 (3 first)Database Systems & Data Management · 2 (1 first)Business Process & Enterprise Data · 1
| Year | Publication | Venue | Position |
|---|---|---|---|
| 2025 | Provoking critical thinking: Using counter-arguments in online discussion summarisationabstractGenerative AI systems based on Large Language Models (LLMs), like ChatGPT, have brought profound convenience to users thanks to their ability to summarise existing documents and to generate new text. This shows the potential to summarise online human discussions or debates for new entrants to quickly comprehend the ongoing matters and arguments and to get efficiently involved in the opinion deliberation process. However, generative AI has frequently been associated with negatively affecting users’ decision making. In this paper, we study a novel approach based on generative AI to trigger users’ critical thinking by challenging fresh counter-arguments after summarising existing online discussions for incoming users. We conduct a user study with 558 participants to determine the effectiveness and fairness of AI summarisation across three online platforms — Reddit, Kialo, and Debatewise. Our results show that the intervention methods and platform differences are strongly associated with participants’ level of opinion change and the strength of their belief. We found that participants’ opinion changes affected their perceived usefulness of the AI system. Our work opens the door to LLM applications helping Web users participate in online opinion deliberation more efficiently, with a higher level of critical thinking, and with a reduced negative attitude. Shangqian Li, Lei Han 0003, Gianluca Demartini |
Inf. Process. Manag. | 2 |
| 2024 | On the Role of Large Language Models in Crowdsourcing Misinformation AssessmentabstractThe proliferation of online misinformation significantly undermines the credibility of web content. Recently, crowd workers have been successfully employed to assess misinformation to address the limited scalability of professional fact-checkers. An alternative approach to crowdsourcing is the use of large language models (LLMs). These models are however also not perfect. In this paper, we investigate the scenario of crowd workers working in collaboration with LLMs to assess misinformation. We perform a study where we ask crowd workers to judge the truthfulness of statements under different conditions: with and without LLMs labels and explanations. Our results show that crowd workers tend to overestimate truthfulness when exposed to LLM-generated information. Crowd workers are misled by wrong LLM labels, but, on the other hand, their self-reported confidence is lower when they make mistakes due to relying on the LLM. We also observe diverse behaviors among crowd workers when the LLM is presented, indicating that leveraging LLMs can be considered a distinct working strategy. Jiechen Xu, Lei Han 0003, Shazia Sadiq, Gianluca Demartini |
ICWSM | 2 |
| 2024 | On the Impact of Showing Evidence from Peers in Crowdsourced Truthfulness AssessmentsabstractMisinformation has been rapidly spreading online. The common approach to dealing with it is deploying expert fact-checkers who follow forensic processes to identify the veracity of statements. Unfortunately, such an approach does not scale well. To deal with this, crowdsourcing has been looked at as an opportunity to complement the work done by trained journalists. In this article, we look at the effect of presenting the crowd with evidence from others while judging the veracity of statements. We implement variants of the judgment task design to understand whether and how the presented evidence may or may not affect the way crowd workers judge truthfulness and their performance. Our results show that, in certain cases, the presented evidence and the way in which it is presented may mislead crowd workers who would otherwise be more accurate if judging independently from others. Those who make appropriate use of the provided evidence, however, can benefit from it and generate better judgments. Jiechen Xu, Lei Han 0003, Shazia Sadiq, Gianluca Demartini |
ACM Trans. Inf. Syst. | 2 |
| 2023 | On the Impact of Data Quality on Image Classification FairnessabstractWith the proliferation of algorithmic decision-making, increased scrutiny has been placed on these systems. This paper explores the relationship between the quality of the training data and the overall fairness of the models trained with such data in the context of supervised classification. We measure key fairness metrics across a range of algorithms over multiple image classification datasets that have a varying level of noise in both the labels and the training data itself. We describe noise in the labels as inaccuracies in the labelling of the data in the training set and noise in the data as distortions in the data, also in the training set. By adding noise to the original datasets, we can explore the relationship between the quality of the training data and the fairness of the output of the models trained on that data. Aki Barry, Lei Han 0003, Gianluca Demartini |
SIGIR | 2 |
| 2023 | Human-in-the-loop Regular Expression Extraction for Single Column Format InconsistencyabstractFormat inconsistency is one of the most frequently appearing data quality issues encountered during data cleaning. Existing automated approaches commonly lack applicability and generalisability, while approaches with human inputs typically require specialized skills such as writing regular expressions. This paper proposes a novel hybrid human-machine system, namely “Data-Scanner-4C”, which leverages crowdsourcing to address syntactic format inconsistencies in a single column effectively. We first ask crowd workers to create examples from single-column data through “data selection” and “result validation” tasks. Then, we propose and use a novel rule-based learning algorithm to infer the regular expressions that propagate formats from created examples to the entire column. Our system integrates crowdsourcing and algorithmic format extraction techniques in a single workflow. Having human experts write regular expressions is no longer required, thereby reducing both the time as well as the opportunity for error. We conducted experiments through both synthetic and real-world datasets, and our results show how the proposed approach is applicable and effective across data types and formats. Shaochen Yu, Lei Han 0003, Marta Indulska, Shazia Sadiq, Gianluca Demartini |
WWW | 2 |
| 2023 | On the role of human and machine metadata in relevance judgment tasks
Jiechen Xu, Lei Han 0003, Shazia Sadiq, Gianluca Demartini |
Inf. Process. Manag. | 2 |
| 2023 | DataOps-4G: On Supporting Generalists in Data Quality DiscoveryabstractData preparation has become a necessary but labor and resource intensive step to perform data analytics. To date, such activities still require considerable manual effort from experts. In this paper, we focus on a specific data preparation activity, namely data quality discovery. We explore different settings in which data workers undertake data quality discovery tasks and the implications of those settings for the efficiency and effectiveness of data workers. To this end, we propose DataOps-4G, a data curation platform for generalists, that allows users to interact with data without the need to write code. We wrap up pre-defined code snippets that implement useful functionalities to explore data quality and bundle the code into so-called DataOps. Then, we conduct a lab-based user study to evaluate our DataOps-4G platform from two perspectives: (i) effectiveness, the accuracy of the outcomes achieved by participants; and (ii) efficiency, their effort and strategies in task completion. Our experimental results uncover how effectiveness and efficiency can be affected by their task completion patterns and strategies. This opens up the possibility of popularizing data curation processes by employing non-experts (e.g., from crowdsourcing platforms) and consequently allowing experts to focus on more complex activities (e.g., building machine learning models). Shaochen Yu, Tianwa Chen, Lei Han 0003, Gianluca Demartini, Shazia Sadiq |
IEEE Trans. Knowl. Data Eng. | 3 |
| 2023 | A Data-Driven Analysis of Behaviors in Data Curation ProcessesabstractUnderstanding how data workers interact with data, and various pieces of information related to data preparation, is key to designing systems that can better support them in exploring datasets. To date, however, there is a paucity of research studying the strategies adopted by data workers as they carry out data preparation activities. In this work, we investigate a specific data preparation activity, namely data quality discovery , and aim to (i) understand the behaviors of data workers in discovering data quality issues, (ii) explore what factors (e.g., prior experience) can affect their behaviors, as well as (iii) understand how these behavioral observations relate to their performance. To this end, we collect a multi-modal dataset through a data-driven experiment that relies on the use of eye-tracking technology with a purpose-designed platform built on top of iPython Notebook. The experiment results reveal that: (i) ‘copy–paste–modify’ is a typical strategy for writing code to complete tasks; (ii) proficiency in writing code has a significant impact on the quality of task performance, while perceived difficulty and efficacy can influence task completion patterns; and (iii) searching in external resources is a prevalent action that can be leveraged to achieve better performance. Furthermore, our experiment indicates that providing sample code within the system can help data workers get started with their task, and surfacing underlying data is an effective way to support exploration. By investigating data worker behaviors prior to each search action, we also find that the most common reasons that trigger external search actions are the need to seek assistance in writing or debugging code and to search for relevant code to reuse. Based on our experiment results, we showcase a systematic approach to select from the top best code snippets created by data workers and assemble them to achieve better performance than the best individual performer in the dataset. By doing so, our findings not only provide insights into patterns of interactions with various system components and information resources when performing data curation tasks, but also build effective and efficient data curation processes through data workers’ collective intelligence. Lei Han 0003, Tianwa Chen, Gianluca Demartini, Marta Indulska, Shazia Sadiq |
ACM Trans. Inf. Syst. | 1 |
| 2022 | A Behavioural Analysis of Metadata Use in Evaluating the Quality of Repurposed Data
Lei Han 0003, Gianluca Demartini, Marta Indulska, Shazia Sadiq |
ER | 2 |
| 2022 | Exploring Data Literacy Levels in the Crowd - the Case of COVID-19
Shaoyang Fan, Lei Han 0003, Gianluca Demartini, Shazia Sadiq |
ICWSM | 2 |
| 2021 | Iterative Human-in-the-Loop Discovery of Unknown Unknowns in Image DatasetsabstractAutomatic predictions (e.g., recognizing objects in images) may result in systematic errors if certain classes are not well represented by training instances (these errors are called unknowns). When a model assigns high confidence scores to these wrong predictions (this type of error is called unknown unknowns), it becomes challenging to automatically identify them. In this paper, we present the first work on leveraging human intelligence to discover unknown unknowns (UUs) in an iterative way. The proposed methodology first differentiates the feature space generated by crowd workers labelling instances (e.g., images) in an active learning fashion from the space learned by the prediction model over a batch training phase, and thus identifies the predictions most likely to be UUs. Next, we add crowd labels collected for these discovered UUs to the training set and re-train the model with this extended dataset. This process is then repeated iteratively to discover more instances of both unknown and under-represented classes. Our experimental results show that the proposed methodology is able to (1) efficiently discover UUs, (2) significantly improve the quality of model predictions, and (3) to push UUs into known unknowns (i.e., the model makes mistakes but at least its classification confidence on those instances is low so those predictions can be discarded or post-processed) for further investigation. We additionally discuss the trade-off between prediction quality improvements and the human effort required to achieve those improvements. Our results bear implications on building cost-effective systems to discover UUs with humans in the loop. Lei Han 0003, Gianluca Demartini |
HCOMP | 1 |
| 2021 | The Impact of Task Abandonment in CrowdsourcingabstractCrowdsourcing has become a standard methodology to collect manually annotated data such as relevance judgments at scale. On crowdsourcing platforms like Amazon MTurk or FigureEight, crowd workers select tasks to work on based on different dimensions such as task reward and requester reputation. Requesters then receive the judgments of workers who self-selected into the tasks and completed them successfully. Several crowd workers, however, preview tasks, begin working on them, reaching varying stages of task completion without finally submitting their work. Such behavior results in unrewarded effort which remains invisible to requesters. In this paper, we conduct an investigation of the phenomenon of task abandonment, the act of workers previewing or beginning a task and deciding not to complete it. We follow a three-fold methodology which includes 1) investigating the prevalence and causes of task abandonment by means of a survey over different crowdsourcing platforms, 2) data-driven analysis of logs collected during a large-scale relevance judgment experiment, and 3) controlled experiments measuring the effect of different dimensions on abandonment. Our results show that task abandonment is a widely spread phenomenon. Apart from accounting for a considerable amount of wasted human effort, this bears important implications on the hourly wages of workers as they are not rewarded for tasks that they do not complete. We also show how task abandonment may have strong implications on the use of collected data (for example, on the evaluation of Information Retrieval systems). Lei Han 0003, Kevin Roitero, Ujwal Gadiraju, Cristina Sarasua, Alessandro Checco, Eddy Maddalena, Gianluca Demartini |
IEEE Trans. Knowl. Data Eng. | 1 |
| 2020 | Modelling User Behavior Dynamics with EmbeddingsabstractUnderstanding user interaction behaviors remains a challenging problem. Quantifying behavior dynamics over time as users complete tasks has only been done in specific domains. In this paper, we present a user behavior model built using behavior embeddings to compare behaviors and their change over time. To this end, we first define the formal model and train the model using both action (e.g., copy/paste) embeddings and user interaction feature (e.g., length of the copied text) embeddings. Having obtained vector representations of user behaviors, we then define three measurements to model behavior dynamics over time, namely: behavior position, displacement, and velocity. To evaluate the proposed methodology, we use three real world datasets: (i) tens of users completing complex data curation tasks in a lab setting, (ii) hundreds of crowd workers completing structured tasks in a crowdsourcing setting, and (iii) thousands of editors completing unstructured editing tasks on Wikidata. Through these datasets, we show that the proposed methodology can: (i) surface behavioral differences among users; (ii) recognize relative behavioral changes; and (iii) discover directional deviations of user behaviors. Our approach can be used (i) to capture behavioral semantics from data in a consistent way, (ii) to quantify behavioral diversity for a task and among different users, and (iii) to explore the temporal behavior evolution with respect to various task properties (e.g., structure and difficulty). Lei Han 0003, Alessandro Checco, Djellel Eddine Difallah, Gianluca Demartini, Shazia Sadiq |
CIKM | 1 |
| 2020 | On Understanding Data Worker Interaction BehaviorsabstractUnderstanding how data workers interact with data and various pieces of information (e.g., code snippet examples) is key to design systems that can better support them in exploring a given dataset. To date, however, there is a paucity of research studying information seeking patterns and the strategies adopted by data workers as they carry out data curation activities. In this work, we aim at understanding the behaviors of data workers in discovering data quality issues, and how these behavioral observations relate to their performance. Specifically, we investigate how data workers use information resources and tools to support their task completion. To this end, we collect a multi-modal dataset through a data-driven experiment that relies on the use of eye-tracking technology with a purpose-designed platform built on top of iPython Notebook. The collected data reveals that: (i) searching in external resources is a prevalent action that can be leveraged to achieve better performance; (ii) 'copy-paste-modify' is a typical strategy for writing code to complete tasks; (iii) providing sample code within the system could help data workers to get started with their task; and (iv) surfacing underlying data is an effective way to support exploration. By investigating the behaviors prior to each search action, we also find that the most common reasons that trigger external search actions are the need to seek assistance in writing or debugging code and to search for relevant code to reuse. Our findings provide insights into patterns of interactions with various system components and information resources to perform data curation tasks. This bears implications on the design of domain-specific IR systems for data workers like code-base search. Lei Han 0003, Tianwa Chen, Gianluca Demartini, Marta Indulska, Shazia Sadiq |
SIGIR | 1 |
| 2020 | When the Human is in the Loop: Cost, Effort and BehaviorabstractData from human-machine interaction can be used to improve the quality of artificial intelligence (AI) systems. When designing a system with humans in the loop, one of the questions to be asked is how much human work is required to create a reliable data collection. Crowdsourcing has become a popular methodology to collect annotations from crowd workers who successfully complete crowdsourcing tasks. Thus, if workers reach varying task completion stages without finally submitting their work, all their effort would be unrewarded and annotations discarded. Task abandonment remains invisible within the platform. On the other hand, paid crowdsourcing dynamics are often influenced by large batches of similar tasks, allowing workers to learn and develop efficient work strategies. To date, however, there is limited research aiming at understanding how human annotators complete tasks over time. Even for complex tasks in lab studies, understanding how behavioral patterns evolve during task completion remains unexplored. Lei Han 0003 |
SIGIR | 1 |
| 2020 | Crowd Worker Strategies in Relevance Judgment TasksabstractCrowdsourcing is a popular technique to collect large amounts of human-generated labels, such as relevance judgments used to create information retrieval (IR) evaluation collections. Previous research has shown how collecting high quality labels from a crowdsourcing platform can be challenging. Existing quality assurance techniques focus on answer aggregation or on the use of gold questions where ground-truth data allows to check for the quality of the responses. Lei Han 0003, Eddy Maddalena, Alessandro Checco, Cristina Sarasua, Ujwal Gadiraju, Kevin Roitero, Gianluca Demartini |
WSDM | 1 |
| 2019 | On Transforming Relevance ScalesabstractInformation Retrieval (IR) researchers have often used existing IR evaluation collections and transformed the relevance scale in which judgments have been collected, e.g., to use metrics that assume binary judgments like Mean Average Precision. Such scale transformations are often arbitrary (e.g., 0,1 mapped to 0 and 2,3 mapped to 1) and it is assumed that they have no impact on the results of IR evaluation. Moreover, the use of crowdsourcing to collect relevance judgments has become a standard methodology. When designing the crowdsourcing relevance judgment task, one of the decision to be made is the how granular the relevance scale used to collect judgments should be. Such decision has then repercussions on the metrics used to measure IR system effectiveness. In this paper we look at the effect of scale transformations in a systematic way. We perform extensive experiments to study the transformation of judgments from fine-grained to coarse-grained. We use different relevance judgments expressed on different relevance scales and either expressed by expert annotators or collected by means of crowdsourcing. The objective is to understand the impact of relevance scale transformations on IR evaluation outcomes and to draw conclusions on how to best transform judgments into a different scale, when necessary. Lei Han 0003, Kevin Roitero, Eddy Maddalena, Stefano Mizzaro, Gianluca Demartini |
CIKM | 1 |
| 2019 | All Those Wasted Hours: On Task Abandonment in CrowdsourcingabstractCrowdsourcing has become a standard methodology to collect manually annotated data such as relevance judgments at scale. On crowdsourcing platforms like Amazon MTurk or FigureEight, crowd workers select tasks to work on based on different dimensions such as task reward and requester reputation. Requesters then receive the judgments of workers who self-selected into the tasks and completed them successfully. Several crowd workers, however, preview tasks, begin working on them, reaching varying stages of task completion without finally submitting their work. Such behavior results in unrewarded effort which remains invisible to requesters. In this paper, we conduct the first investigation into the phenomenon of task abandonment, the act of workers previewing or beginning a task and deciding not to complete it. We follow a three-fold methodology which includes 1) investigating the prevalence and causes of task abandonment by means of a survey over different crowdsourcing platforms, 2) data-driven analyses of logs collected during a large-scale relevance judgment experiment, and 3) controlled experiments measuring the effect of different dimensions on abandonment. Our results show that task abandonment is a widely spread phenomenon. Apart from accounting for a considerable amount of wasted human effort, this bears important implications on the hourly wages of workers as they are not rewarded for tasks that they do not complete. We also show how task abandonment may have strong implications on the use of collected data (for example, on the evaluation of IR systems). Lei Han 0003, Kevin Roitero, Ujwal Gadiraju, Cristina Sarasua, Alessandro Checco, Eddy Maddalena, Gianluca Demartini |
WSDM | 1 |
| 2018 | API Caveat Explorer - Surfacing Negative Usages from Practice: An API-oriented Interactive Exploratory Search System for ProgrammersabstractApplication programming interface (API) documentation well describes an API and how to use it. However, official documentation does not describe "how not to use it" or the different kinds of errors when an API is used wrongly. Programming caveats are negative usages of an API. When these caveats are overlooked, errors may emerge, leading to heavy discussions on Q&A websites like Stack Overflow. In this demonstration, we present API Caveat Explorer, a search system to explore API caveats that are mined from large-scale unstructured discussions on Stack Overflow. API Caveat Explorer takes API-oriented queries such as "HashMap" and retrieves API caveats by text summarization techniques. API caveats are represented by sentences, which are context-independent, prominent, semantically diverse and non-redundant. The system provides a web-based interface that allows users to interactively explore the full picture of all discovered caveats of an API, and the details of each. The potential users of API Caveat Explorer are programmers and educators for learning and teaching APIs. Jing Li 0034, Aixin Sun, Zhenchang Xing, Lei Han 0003 |
SIGIR | 4 |