Bojan Karlas

dblp:185/0781 · DBLP profile ↗
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17ranked-venue papers
5as first author
9since 2021 · last 2025
0000-0002-6462-3579ORCID · verified

Domains — the database's venue-derived domains; a paper can count in several

Databases, data management, data science and information retrieval · 8 · 4 first-author · 4 since 2021Artificial intelligence and machine learning · 6 · 2 first-author · 4 since 2021Security and privacy · 2 · 1 since 2021Systems, architecture and hardware · 1Computer networks · 1
YearPublicationVenuePosition
2025 Navigating Data Errors in Machine Learning Pipelines: Identify, Debug, and Learn
abstract
Addressing data errors such as wrong, missing, noisy, biased, or out-of-distribution values has become a crucial part of the machine learning (ML) development lifecycle. Un-fortunately, traditional approaches have relied either on treating the symptom by refining the model architecture, or on improving data quality by repairing incorrect values regardless of their significance to the downstream model. Both strategies end up tackling the problem in isolation, and disregard the structure of modern ML pipelines, which involve a series of steps for data preprocessing, model training, and prediction processing. Consequently, they miss the opportunity to consider how different data errors propagate through the pipeline and how they impact its ability to perform downstream tasks. In recent years, the research community has made significant strides towards more holistic approaches for identifying the most harmful data errors, performing the most beneficial repairs, and ensuring reliable performance even if some data errors remain present. This tutorial will survey some prominent work published in this space and showcase several tools that have been developed. By combining theoretical foundations with practical demonstrations, attendees will gain actionable strategies to diagnose and mitigate data quality issues, improving the reliability, fairness, and transparency of ML systems in real-world settings.
Bojan Karlas, Babak Salimi, Sebastian Schelter
ICDE1
2025 Scalable Data Debugging for Neighborhood-based Recommendation with Data Shapley Values
Barrie Kersbergen, Olivier Sprangers, Bojan Karlas, Maarten de Rijke, Sebastian Schelter
RecSys3
2024 Data Debugging with Shapley Importance over Machine Learning Pipelines
abstract
When a machine learning (ML) model exhibits poor quality (e.g., poor accuracy or fairness), the problem can often be traced back to errors in the training data. Being able to discover the data examples that are the most likely culprits is a fundamental concern that has received a lot of attention recently. One prominent way to measure "data importance" with respect to model quality is the Shapley value. Unfortunately, existing methods only focus on the ML model in isolation, without considering the broader ML pipeline for data preparation and feature extraction, which appears in the majority of real-world ML code. This presents a major limitation to applying existing methods in practical settings. In this paper, we propose Datascope, a method for efficiently computing Shapley-based data importance over ML pipelines. We introduce several approximations that lead to dramatic improvements in terms of computational speed. Finally, our experimental evaluation demonstrates that our methods are capable of data error discovery that is as effective as existing Monte Carlo baselines, and in some cases even outperform them. We release our code as an open-source data debugging library available at https://github.com/easeml/datascope.
Bojan Karlas, David Dao, Matteo Interlandi, Sebastian Schelter, Wentao Wu 0001, Ce Zhang 0001
ICLR1
2023 DataPerf: Benchmarks for Data-Centric AI Development
abstract
Machine learning research has long focused on models rather than datasets, and prominent datasets are used for common ML tasks without regard to the breadth, difficulty, and faithfulness of the underlying problems. Neglecting the fundamental importance of data has given rise to inaccuracy, bias, and fragility in real-world applications, and research is hindered by saturation across existing dataset benchmarks. In response, we present DataPerf, a community-led benchmark suite for evaluating ML datasets and data-centric algorithms. We aim to foster innovation in data-centric AI through competition, comparability, and reproducibility. We enable the ML community to iterate on datasets, instead of just architectures, and we provide an open, online platform with multiple rounds of challenges to support this iterative development. The first iteration of DataPerf contains five benchmarks covering a wide spectrum of data-centric techniques, tasks, and modalities in vision, speech, acquisition, debugging, and diffusion prompting, and we support hosting new contributed benchmarks from the community. The benchmarks, online evaluation platform, and baseline implementations are open source, and the MLCommons Association will maintain DataPerf to ensure long-term benefits to academia and industry.
Mark Mazumder, Colby R. Banbury, Xiaozhe Yao, Bojan Karlas, William Gaviria Rojas, Sudnya Frederick Diamos, Gregory Frederick Diamos, Lynn He, Alicia Parrish, Hannah Kirk, Jessica Quaye, Charvi Rastogi, Douwe Kiela, David Jurado, David Kanter, Rafael Mosquera, Will Cukierski, Juan Ciro, Lora Aroyo, Bilge Acun, Lingjiao Chen, Mehul Raje, Max Bartolo, Sabri Eyuboglu, Amirata Ghorbani, Emmett D. Goodman, Addison Howard, Oana Inel, Tariq Kane, Christine R. Kirkpatrick, D. Sculley, Tzu-Sheng Kuo, Jonas Mueller 0001, Tristan Thrush, Joaquin Vanschoren, Margaret Warren, Adina Williams, Serena Yeung-Levy, Newsha Ardalani, Praveen K. Paritosh, Ce Zhang 0001, James Zou 0001, Carole-Jean Wu, Cody Coleman, Andrew Y. Ng, Peter Mattson, Vijay Janapa Reddi
NeurIPS4
2023 RAB: Provable Robustness Against Backdoor Attacks
abstract
Recent studies have shown that deep neural net-works (DNNs) are vulnerable to adversarial attacks, including evasion and backdoor (poisoning) attacks. On the defense side, there have been intensive efforts on improving both empirical and provable robustness against evasion attacks; however, the provable robustness against backdoor attacks still remains largely unexplored. In this paper, we focus on certifying the machine learning model robustness against general threat models, especially backdoor attacks. We first provide a unified framework via randomized smoothing techniques and show how it can be instantiated to certify the robustness against both evasion and backdoor attacks. We then propose the first robust training process, RAB, to smooth the trained model and certify its robustness against backdoor attacks. We theoretically prove the robustness bound for machine learning models trained with RAB and prove that our robustness bound is tight. In addition, we theoretically show that it is possible to train the robust smoothed models efficiently for simple models such as K-nearest neighbor classifiers, and we propose an exact smooth-training algorithm that eliminates the need to sample from a noise distribution for such models. Empirically, we conduct comprehensive experiments for different machine learning (ML) models such as DNNs, support vector machines, and K-NN models on MNIST, CIFAR-10, and ImageNette datasets and provide the first benchmark for certified robustness against backdoor attacks. In addition, we evaluate K-NN models on a spambase tabular dataset to demonstrate the advantages of the proposed exact algorithm. Both the theoretic analysis and the comprehensive evaluation on diverse ML models and datasets shed light on further robust learning strategies against general training time attacks.
Maurice Weber, Bojan Karlas, Ce Zhang 0001, Bo Li 0026
SP3
2022 Screening Native Machine Learning Pipelines with ArgusEyes
Sebastian Schelter, Stefan Grafberger, Shubha Guha, Olivier Sprangers, Bojan Karlas, Ce Zhang 0001
CIDR5
2022 Improving Certified Robustness via Statistical Learning with Logical Reasoning
abstract
Intensive algorithmic efforts have been made to enable the rapid improvements of certificated robustness for complex ML models recently. However, current robustness certification methods are only able to certify under a limited perturbation radius. Given that existing pure data-driven statistical approaches have reached a bottleneck, in this paper, we propose to integrate statistical ML models with knowledge (expressed as logical rules) as a reasoning component using Markov logic networks (MLN), so as to further improve the overall certified robustness. This opens new research questions about certifying the robustness of such a paradigm, especially the reasoning component (e.g., MLN). As the first step towards understanding these questions, we first prove that the computational complexity of certifying the robustness of MLN is #P-hard. Guided by this hardness result, we then derive the first certified robustness bound for MLN by carefully analyzing different model regimes. Finally, we conduct extensive experiments on five datasets including both high-dimensional images and natural language texts, and we show that the certified robustness with knowledge-based logical reasoning indeed significantly outperforms that of the state-of-the-arts.
Zhikuan Zhao, Boxin Wang, Jiawei Zhang 0013, Linyi Li 0001, Hengzhi Pei, Bojan Karlas, Ji Liu 0002, Heng Guo 0001, Ce Zhang 0001, Bo Li 0026
NeurIPS7
2021 Online Active Model Selection for Pre-trained Classifiers
abstract
Given $k$ pre-trained classifiers and a stream of unlabeled data examples, how can we actively decide when to query a label so that we can distinguish the best model from the rest while making a small number of queries? Answering this question has a profound impact on a range of practical scenarios. In this work, we design an online selective sampling approach that actively selects informative examples to label and outputs the best model with high probability at any round. Our algorithm can also be used for online prediction tasks for both adversarial and stochastic streams. We establish several theoretical guarantees for our algorithm and extensively demonstrate its effectiveness in our experimental studies.
Mohammad Reza Karimi, Nezihe Merve Gürel, Bojan Karlas, Johannes Rausch, Ce Zhang 0001, Andreas Krause 0001
AISTATS3
2021 Ease.ML: A Lifecycle Management System for Machine Learning
Leonel Aguilar Melgar, David Dao, Shaoduo Gan, Nezihe Merve Gürel, Nora Hollenstein, Jiawei Jiang 0001, Bojan Karlas, Thomas Lemmin, Tian Li 0005, Yang Li 0106, Susie Xi Rao, Johannes Rausch, Cédric Renggli, Luka Rimanic, Maurice Weber, Shuai Zhang 0007, Zhikuan Zhao, Kevin Schawinski, Wentao Wu 0001, Ce Zhang 0001
CIDR7
2020 Building Continuous Integration Services for Machine Learning
abstract
Continuous integration (CI) has been a de facto standard for building industrial-strength software. Yet, there is little attention towards applying CI to the development of machine learning (ML) applications until the very recent effort on the theoretical side. In this paper, we take a step forward to bring the theory into practice.
Bojan Karlas, Matteo Interlandi, Cédric Renggli, Wentao Wu 0001, Ce Zhang 0001, Deepak Mukunthu Iyappan Babu, Jordan Edwards, Chris Lauren, Andy Xu, Markus Weimer
KDD1
2020 Nearest Neighbor Classifiers over Incomplete Information: From Certain Answers to Certain Predictions
abstract
Machine learning (ML) applications have been thriving recently, largely attributed to the increasing availability of data. However, inconsistency and incomplete information are ubiquitous in real-world datasets, and their impact on ML applications remains elusive. In this paper, we present a formal study of this impact by extending the notion of Certain Answers for Codd tables , which has been explored by the database research community for decades, into the field of machine learning. Specifically, we focus on classification problems and propose the notion of "Certain Predictions" (CP) --- a test data example can be certainly predicted (CP'ed) if all possible classifiers trained on top of all possible worlds induced by the incompleteness of data would yield the same prediction. We study two fundamental CP queries: (Q1) checking query that determines whether a data example can be CP'ed; and (Q2) counting query that computes the number of classifiers that support a particular prediction (i.e., label). Given that general solutions to CP queries are, not surprisingly, hard without assumption over the type of classifier, we further present a case study in the context of nearest neighbor (NN) classifiers, where efficient solutions to CP queries can be developed --- we show that it is possible to answer both queries in linear or polynomial time over exponentially many possible worlds. We demonstrate one example use case of CP in the important application of "data cleaning for machine learning (DC for ML)." We show that our proposed CPClean approach built based on CP can often significantly outperform existing techniques, particularly on datasets with systematic missing values. For example, on 5 datasets with systematic missingness, CPClean (with early termination) closes 100% gap on average by cleaning 36% of dirty data on average, while the best automatic cleaning approach BoostClean can only close 14% gap on average.
Bojan Karlas, Peng Li 0062, Renzhi Wu, Nezihe Merve Gürel, Xu Chu 0002, Wentao Wu 0001, Ce Zhang 0001
Proc. VLDB Endow.1
2019 AutoML from Service Provider's Perspective: Multi-device, Multi-tenant Model Selection with GP-EI
abstract
AutoML has become a popular service that is provided by most leading cloud service providers today. In this paper, we focus on the AutoML problem from the \emph{service provider’s perspective}, motivated by the following practical consideration: When an AutoML service needs to serve {\em multiple users} with {\em multiple devices} at the same time, how can we allocate these devices to users in an efficient way? We focus on GP-EI, one of the most popular algorithms for automatic model selection and hyperparameter tuning, used by systems such as Google Vizer. The technical contribution of this paper is the first multi-device, multi-tenant algorithm for GP-EI that is aware of \emph{multiple} computation devices and multiple users sharing the same set of computation devices. Theoretically, given $N$ users and $M$ devices, we obtain a regret bound of $O((\text{\bf {MIU}}(T,K) + M)\frac{N^2}{M})$, where $\text{\bf {MIU}}(T,K)$ refers to the maximal incremental uncertainty up to time $T$ for the covariance matrix $K$. Empirically, we evaluate our algorithm on two applications of automatic model selection, and show that our algorithm significantly outperforms the strategy of serving users independently. Moreover, when multiple computation devices are available, we achieve near-linear speedup when the number of users is much larger than the number of devices.
Chen Yu 0009, Bojan Karlas, Ce Zhang 0001, Ji Liu 0002
AISTATS2
2019 Is advance knowledge of flow sizes a plausible assumption?
Vojislav Dukic, Sangeetha Abdu Jyothi, Bojan Karlas, Muhsen Owaida, Ce Zhang 0001, Ankit Singla
NSDI3
2019 Ease.ml/ci and Ease.ml/meter in Action: Towards Data Management for Statistical Generalization
abstract
Developing machine learning (ML) applications is similar to developing traditional software --- it is often an iterative process in which developers navigate within a rich space of requirements, design decisions, implementations, empirical quality , and performance . In traditional software development, software engineering is the field of study which provides principled guidelines for this iterative process. However, as of today, the counterpart of "software engineering for ML" is largely missing --- developers of ML applications are left with powerful tools (e.g., TensorFlow and PyTorch) but little guidance regarding the development lifecycle itself. In this paper, we view the management of ML development life-cycles from a data management perspective. We demonstrate two closely related systems, ease.ml/ci and ease.ml/meter, that provide some "principled guidelines" for ML application development: ci is a continuous integration engine for ML models and meter is a "profiler" for controlling overfitting of ML models. Both systems focus on managing the "statistical generalization power" of datasets used for assessing the quality of ML applications, namely, the validation set and the test set . By demonstrating these two systems we hope to spawn further discussions within our community on building this new type of data management systems for statistical generalization.
Cédric Renggli, Frances Ann Hubis, Bojan Karlas, Kevin Schawinski, Wentao Wu 0001, Ce Zhang 0001
Proc. VLDB Endow.3
2018 Network Scheduling in the Dark
abstract
No abstract available.
Vojislav Dukic, Sangeetha Abdu Jyothi, Bojan Karlas, Muhsen Owaida, Ce Zhang 0001, Ankit Singla
SoCC3
2018 Ease.ml in Action: Towards Multi-tenant Declarative Learning Services
abstract
We demonstrate ease.ml, a multi-tenant machine learning service we host at ETH Zurich for various research groups. Unlike existing machine learning services, ease.ml presents a novel architecture that supports multi-tenant, cost-aware model selection that optimizes for minimizing total regrets of all users. Moreover, it provides a novel user interface that enables declarative machine learning at a higher level: Users only need to specify the input/output schemata of their learning tasks and ease.ml can handle the rest. In this demonstration, we present the design principles of ease.ml, highlight the implementation of its key components, and showcase how ease.ml can help ease machine learning tasks that often perplex even experienced users.
Bojan Karlas, Ji Liu 0002, Wentao Wu 0001, Ce Zhang 0001
Proc. VLDB Endow.1
2016 The Curious Case of the PDF Converter that Likes Mozart: Dissecting and Mitigating the Privacy Risk of Personal Cloud Apps
abstract
Abstract Third party apps that work on top of personal cloud services, such as Google Drive and Drop-box, require access to the user’s data in order to provide some functionality. Through detailed analysis of a hundred popular Google Drive apps from Google’s Chrome store, we discover that the existing permission model is quite often misused: around two-thirds of analyzed apps are over-privileged, i.e., they access more data than is needed for them to function. In this work, we analyze three different permission models that aim to discourage users from installing over-privileged apps. In experiments with 210 real users, we discover that the most successful permission model is our novel ensemble method that we call Far-reaching Insights. Far-reaching Insights inform the users about the data-driven insights that apps can make about them (e.g., their topics of interest, collaboration and activity patterns etc.) Thus, they seek to bridge the gap between what third parties can actually know about users and users’ perception of their privacy leakage. The efficacy of Far-reaching Insights in bridging this gap is demonstrated by our results, as Far-reaching Insights prove to be, on average, twice as effective as the current model in discouraging users from installing over-privileged apps. In an effort to promote general privacy awareness, we deployed PrivySeal, a publicly available privacy-focused app store that uses Far-reaching Insights. Based on the knowledge extracted from data of the store’s users (over 115 gigabytes of Google Drive data from 1440 users with 662 installed apps), we also delineate the ecosystem for 3rd party cloud apps from the standpoint of developers and cloud providers. Finally, we present several general recommendations that can guide other future works in the area of privacy for the cloud. To the best of our knowledge, ours is the first work that tackles the privacy risk posed by 3rd party apps on cloud platforms in such depth.
Hamza Harkous, Rameez Rahman, Bojan Karlas, Karl Aberer
Proc. Priv. Enhancing Technol.3