流数据分类的重要问题之一是概念漂移的发生，包括分类任务的概率特征的变化。这种现象不稳定了分类模型的性能，并严重降低了其质量。需要抵消这种现象的适当策略来使分类器适应变化的概率特征。实现此类解决方案的一个重要问题是访问数据标签。它通常是昂贵的，从而最大限度地减少与该过程相关的费用，提出了基于半监督学习的学习策略，例如，采用主动学习方法，该方法指示哪些传入对象是有价值的，以便标记为提高分类器的性能。本文提出了一种基于基于分类器集合学习的非静止数据流的基于块的方法，以及考虑可以成功应用于任何数据流分类算法的有限预算的主动学习策略。已经通过使用真实和生成的数据流进行了计算机实验来评估所提出的方法。结果证实了最先进的方法的高质量。

挖掘数据流姿势存在许多挑战，包括数据的连续和非静止性质，待处理的大量信息和限制计算资源。虽然在文献中提出了一些针对这个问题的监督解决方案，但大多数人都假定访问地面真理（以类标签的形式）是无限的，并且在更新学习系统时可以立即使用此类信息。这远非现实，因为必须考虑获取标签的基本成本。因此，需要解决流方案中实际真相要求的解决方案。在本文中，通过组合来自主动学习和自我标签的信息，提出了一种用于预算的挖水数据流的新框架。我们介绍了几种策略，可以利用智能实例选择和半监督程序，同时考虑到概念漂移的潜在存在。这种混合方法允许有效的探索和利用在现实标记预算中的流数据结构。由于我们的框架工作为包装器，因此它可以应用于不同的学习算法。实验研究，在具有各种类型的概念漂移的多样化现实数据流中进行的实验研究，证明了在处理对类标签的高度限制时拟议的策略的有用性。当一个人不能增加标签或更换低效分类器的预算时，呈现的混合方法尤其可行。我们为我们的战略提供了一套关于适用性领域的建议。

Concept drift describes unforeseeable changes in the underlying distribution of streaming data over time. Concept drift research involves the development of methodologies and techniques for drift detection, understanding and adaptation. Data analysis has revealed that machine learning in a concept drift environment will result in poor learning results if the drift is not addressed. To help researchers identify which research topics are significant and how to apply related techniques in data analysis tasks, it is necessary that a high quality, instructive review of current research developments and trends in the concept drift field is conducted. In addition, due to the rapid development of concept drift in recent years, the methodologies of learning under concept drift have become noticeably systematic, unveiling a framework which has not been mentioned in literature. This paper reviews over 130 high quality publications in concept drift related research areas, analyzes up-to-date developments in methodologies and techniques, and establishes a framework of learning under concept drift including three main components: concept drift detection, concept drift understanding, and concept drift adaptation. This paper lists and discusses 10 popular synthetic datasets and 14 publicly available benchmark datasets used for evaluating the performance of learning algorithms aiming at handling concept drift. Also, concept drift related research directions are covered and discussed. By providing state-of-the-art knowledge, this survey will directly support researchers in their understanding of research developments in the field of learning under concept drift.

Concept drift primarily refers to an online supervised learning scenario when the relation between the input data and the target variable changes over time. Assuming a general knowledge of supervised learning in this paper we characterize adaptive learning process, categorize existing strategies for handling concept drift, overview the most representative, distinct and popular techniques and algorithms, discuss evaluation methodology of adaptive algorithms, and present a set of illustrative applications. The survey covers the different facets of concept drift in an integrated way to reflect on the existing scattered state-of-the-art. Thus, it aims at providing a comprehensive introduction to the concept drift adaptation for researchers, industry analysts and practitioners.

近年来，随着传感器和智能设备的广泛传播，物联网（IoT）系统的数据生成速度已大大增加。在物联网系统中，必须经常处理，转换和分析大量数据，以实现各种物联网服务和功能。机器学习（ML）方法已显示出其物联网数据分析的能力。但是，将ML模型应用于物联网数据分析任务仍然面临许多困难和挑战，特别是有效的模型选择，设计/调整和更新，这给经验丰富的数据科学家带来了巨大的需求。此外，物联网数据的动态性质可能引入概念漂移问题，从而导致模型性能降解。为了减少人类的努力，自动化机器学习（AUTOML）已成为一个流行的领域，旨在自动选择，构建，调整和更新机器学习模型，以在指定任务上实现最佳性能。在本文中，我们对Automl区域中模型选择，调整和更新过程中的现有方法进行了审查，以识别和总结将ML算法应用于IoT数据分析的每个步骤的最佳解决方案。为了证明我们的发现并帮助工业用户和研究人员更好地实施汽车方法，在这项工作中提出了将汽车应用于IoT异常检测问题的案例研究。最后，我们讨论并分类了该领域的挑战和研究方向。

Automated Machine Learning (AutoML) has been used successfully in settings where the learning task is assumed to be static. In many real-world scenarios, however, the data distribution will evolve over time, and it is yet to be shown whether AutoML techniques can effectively design online pipelines in dynamic environments. This study aims to automate pipeline design for online learning while continuously adapting to data drift. For this purpose, we design an adaptive Online Automated Machine Learning (OAML) system, searching the complete pipeline configuration space of online learners, including preprocessing algorithms and ensembling techniques. This system combines the inherent adaptation capabilities of online learners with the fast automated pipeline (re)optimization capabilities of AutoML. Focusing on optimization techniques that can adapt to evolving objectives, we evaluate asynchronous genetic programming and asynchronous successive halving to optimize these pipelines continually. We experiment on real and artificial data streams with varying types of concept drift to test the performance and adaptation capabilities of the proposed system. The results confirm the utility of OAML over popular online learning algorithms and underscore the benefits of continuous pipeline redesign in the presence of data drift.

The literature on machine learning in the context of data streams is vast and growing. However, many of the defining assumptions regarding data-stream learning tasks are too strong to hold in practice, or are even contradictory such that they cannot be met in the contexts of supervised learning. Algorithms are chosen and designed based on criteria which are often not clearly stated, for problem settings not clearly defined, tested in unrealistic settings, and/or in isolation from related approaches in the wider literature. This puts into question the potential for real-world impact of many approaches conceived in such contexts, and risks propagating a misguided research focus. We propose to tackle these issues by reformulating the fundamental definitions and settings of supervised data-stream learning with regard to contemporary considerations of concept drift and temporal dependence; and we take a fresh look at what constitutes a supervised data-stream learning task, and a reconsideration of algorithms that may be applied to tackle such tasks. Through and in reflection of this formulation and overview, helped by an informal survey of industrial players dealing with real-world data streams, we provide recommendations. Our main emphasis is that learning from data streams does not impose a single-pass or online-learning approach, or any particular learning regime; and any constraints on memory and time are not specific to streaming. Meanwhile, there exist established techniques for dealing with temporal dependence and concept drift, in other areas of the literature. For the data streams community, we thus encourage a shift in research focus, from dealing with often-artificial constraints and assumptions on the learning mode, to issues such as robustness, privacy, and interpretability which are increasingly relevant to learning in data streams in academic and industrial settings.

异常值是一个事件或观察，其被定义为不同于距群体的不规则距离的异常活动，入侵或可疑数据点。然而，异常事件的定义是主观的，取决于应用程序和域（能量，健康，无线网络等）。重要的是要尽可能仔细地检测异常事件，以避免基础设施故障，因为异常事件可能导致对基础设施的严重损坏。例如，诸如微电网的网络物理系统的攻击可以发起电压或频率不稳定性，从而损坏涉及非常昂贵的修复的智能逆变器。微电网中的不寻常活动可以是机械故障，行为在系统中发生变化，人体或仪器错误或恶意攻击。因此，由于其可变性，异常值检测（OD）是一个不断增长的研究领域。在本章中，我们讨论了使用AI技术的OD方法的进展。为此，通过多个类别引入每个OD模型的基本概念。广泛的OD方法分为六大类：基于统计，基于距离，基于密度的，基于群集的，基于学习的和合奏方法。对于每个类别，我们讨论最近最先进的方法，他们的应用领域和表演。之后，关于对未来研究方向的建议提供了关于各种技术的优缺点和挑战的简要讨论。该调查旨在指导读者更好地了解OD方法的最新进展，以便保证AI。

通常，机器学习应用程序必须应对动态环境，其中数据以潜在无限长度和瞬态行为的连续数据流的形式收集。与传统（批量）数据挖掘相比，流处理算法对计算资源和对数据演进的适应性具有额外要求。它们必须逐步处理实例，因为数据的连续流量禁止存储多次通过的数据。合奏学习在这种情况下取​​得了显着的预测性能。实现为一组（几个）个别分类器，合奏是自然可用于任务并行性的。但是，用于捕获概念漂移的增量学习和动态数据结构增加了缓存未命中并阻碍了并行性的好处。本文提出了一种迷你批处理策略，可以改善多核环境中用于流挖掘的多个集合算法的内存访问局部性和性能。借助正式框架，我们证明迷你批量可以显着降低重用距离（以及缓存未命中的数量）。在六种不同的最先进的集合算法上应用四个基准数据集的六种不同特性的实验显示了8个核心处理器上高达5倍的加速。这些效益牺牲了预测性能的少量减少。

服务监视应用程序不断生成数据以监视其可用性。因此，实时和准确地对传入数据进行分类至关重要。为此，我们的研究开发了一种使用Learn ++来处理不断发展的数据分布的自适应分类方法。这种方法顺序预测并使用新数据更新监视模型，逐渐忘记了过去的知识并确定了突然的概念漂移。我们采用从工业应用获得的连续数据块来逐步评估预测变量的性能。

概念漂移过程挖掘（PM）是一种挑战，因为古典方法假设进程处于稳态，即事件共享相同的进程版本。我们对这些领域的交叉点进行了系统的文献综述，从而审查了过程采矿中的概念漂移，并提出了用于漂移检测和在线流程挖掘的现有技术的分类，以实现不断发展的环境。现有的作品描绘了（i）PM仍然主要关注离线分析，并且（ii）由于缺乏公共评估协议，数据集和指标，过程中的概念漂移技术的评估是麻烦的。

数据流分类是机器学习领域的重要问题。由于数据的非平稳性，其基础分布会随着时间的流逝而变化（概念漂移），因此该模型需要不断适应新的数据统计信息。基于流的主动学习（AL）方法通过交互式查询人类专家以在有限的预算内为最新样本提供新的数据标签来解决此问题。现有的AL策略假设可以立即可用标签，而在现实情况下，专家需要时间提供查询标签（验证延迟），而当请求的标签到达时，它们可能不再相关。在本文中，我们研究了在AL方法上存在概念漂移的情况下，有限，时间变化和未知验证延迟的影响。我们提出了繁殖（PR），这是一种独立的延迟效用估计器，它也预测了所请求但尚不清楚的标签。此外，我们提出了一种依赖漂移的动态预算策略，该策略在检测到的漂移后使用标签预算的可变分布。彻底的实验评估，包括合成和现实世界的非平稳数据集，以及验证延迟和预算的不同设置。我们从经验上表明，所提出的方法始终优于最先进的方法。此外，我们证明，随着时间的及时预算分配，可以提高AL策略的性能，而不会增加整体标签预算。

Fairness-aware mining of massive data streams is a growing and challenging concern in the contemporary domain of machine learning. Many stream learning algorithms are used to replace humans at critical decision-making points e.g., hiring staff, assessing credit risk, etc. This calls for handling massive incoming information with minimum response delay while ensuring fair and high quality decisions. Recent discrimination-aware learning methods are optimized based on overall accuracy. However, the overall accuracy is biased in favor of the majority class; therefore, state-of-the-art methods mainly diminish discrimination by partially or completely ignoring the minority class. In this context, we propose a novel adaptation of Na\"ive Bayes to mitigate discrimination embedded in the streams while maintaining high predictive performance for both the majority and minority classes. Our proposed algorithm is simple, fast, and attains multi-objective optimization goals. To handle class imbalance and concept drifts, a dynamic instance weighting module is proposed, which gives more importance to recent instances and less importance to obsolete instances based on their membership in minority or majority class. We conducted experiments on a range of streaming and static datasets and deduced that our proposed methodology outperforms existing state-of-the-art fairness-aware methods in terms of both discrimination score and balanced accuracy.

近年来，在线增量学习中兴趣增长。然而，这方面存在三个主要挑战。第一个主要困难是概念漂移，即流数据中的概率分布会随着数据到达而改变。第二个重大困难是灾难性的遗忘，即忘记在学习新知识之前学到的东西。我们经常忽略的最后一个是学习潜在的代表。只有良好的潜在表示可以提高模型的预测准确性。我们的研究在此观察中建立并试图克服这些困难。为此，我们提出了一种适应性在线增量学习，用于不断发展数据流（AOL）。我们使用带内存模块的自动编码器，一方面，我们获得了输入的潜在功能，另一方面，根据自动编码器的重建丢失与内存模块，我们可以成功检测存在的存在概念漂移并触发更新机制，调整模型参数及时。此外，我们划分从隐藏层的激活导出的特征，分为两个部分，用于分别提取公共和私有特征。通过这种方法，该模型可以了解新的即将到来的实例的私有功能，但不要忘记我们在过去（共享功能）中学到的内容，这减少了灾难性遗忘的发生。同时，要获取融合特征向量，我们使用自我关注机制来有效地融合提取的特征，这进一步改善了潜在的代表学习。

随着复杂的机器学习模型越来越多地用于银行，交易或信用评分等敏感应用中，对可靠的解释机制的需求越来越不断增长。局部特征归因方法已成为事后和模型不足的解释的流行技术。但是，归因方法通常假设一个固定环境，其中预测模型已经受过训练并保持稳定。结果，通常不清楚本地归因在现实，不断发展的设置（例如流和在线应用程序）中的行为。在本文中，我们讨论了时间变化对本地特征归因的影响。特别是，我们表明，每次更新预测模型或概念漂移都会改变数据生成分布时，本地归因都会变得过时。因此，数据流中的局部特征归因只有在结合一种机制结合使用的机制时才能提供高解释性功能，该机制使我们能够随着时间的推移检测和响应局部变化。为此，我们介绍了Cdleeds，这是一个灵活而模型的不合理框架，用于检测局部变化和概念漂移。 CDEREDS是基于归因的解释技术的直观扩展，以识别过时的局部归因并实现更多针对性的重新计算。在实验中，我们还表明，所提出的框架可以可靠地检测到本地和全球概念漂移。因此，我们的工作在在线机器学习中有助于更有意义，更强大的解释性。

部署的机器学习模型面临着随着时间的流逝而改变数据的问题，这一现象也称为概念漂移。尽管现有的概念漂移检测方法已经显示出令人信服的结果，但它们需要真正的标签作为成功漂移检测的先决条件。尤其是在许多实际应用程序场景中，这种工作真实标签中涵盖的情况很少，而且它们的收购价格昂贵。因此，我们引入了一种用于漂移检测，不确定性漂移检测（UDD）的新算法，该算法能够检测到漂移而无需访问真正的标签。我们的方法基于深层神经网络与蒙特卡洛辍学的不确定性估计。通过将ADWIN技术应用于不确定性估计值，并检测到漂移触发预测模型的重新验证，可以检测到随时间变化的结构变化。与基于输入数据的漂移检测相反，我们的方法考虑了当前输入数据对预测模型属性的影响，而不是仅检测输入数据的变化（这可能导致不必要的重新培训）。我们表明，UDD在两个合成和十个现实世界数据集的回归和分类任务方面优于其他最先进的策略。

Label noise is an important issue in classification, with many potential negative consequences. For example, the accuracy of predictions may decrease, whereas the complexity of inferred models and the number of necessary training samples may increase. Many works in the literature have been devoted to the study of label noise and the development of techniques to deal with label noise. However, the field lacks a comprehensive survey on the different types of label noise, their consequences and the algorithms that consider label noise. This paper proposes to fill this gap. First, the definitions and sources of label noise are considered and a taxonomy of the types of label noise is proposed. Second, the potential consequences of label noise are discussed. Third, label noise-robust, label noise cleansing, and label noise-tolerant algorithms are reviewed. For each category of approaches, a short discussion is proposed to help the practitioner to choose the most suitable technique in its own particular field of application. Eventually, the design of experiments is also discussed, what may interest the researchers who would like to test their own algorithms. In this paper, label noise consists of mislabeled instances: no additional information is assumed to be available like e.g. confidences on labels.

分类链是一种用于在多标签分类中建模标签依赖性的有效技术。但是，该方法需要标签的固定静态顺序。虽然理论上，任何顺序都足够了，实际上，该订单对最终预测的质量具有大量影响。动态分类链表示每个实例对分类的想法，可以动态选择预测标签的顺序。这种方法的天真实现的复杂性是禁止的，因为它需要训练一系列分类器，以满足标签的每种可能置换。为了有效地解决这个问题，我们提出了一种基于随机决策树的新方法，该方法可以动态地选择每个预测的标签排序。我们凭经验展示了下一个标签的动态选择，通过在否则不变的随机决策树模型下使用静态排序。 ％和实验环境。此外，我们还展示了基于极端梯度提升树的替代方法，其允许更具目标的动态分级链训练。我们的结果表明，该变体优于随机决策树和其他基于树的多标签分类方法。更重要的是，动态选择策略允许大大加速培训和预测。

Dataset scaling, also known as normalization, is an essential preprocessing step in a machine learning pipeline. It is aimed at adjusting attributes scales in a way that they all vary within the same range. This transformation is known to improve the performance of classification models, but there are several scaling techniques to choose from, and this choice is not generally done carefully. In this paper, we execute a broad experiment comparing the impact of 5 scaling techniques on the performances of 20 classification algorithms among monolithic and ensemble models, applying them to 82 publicly available datasets with varying imbalance ratios. Results show that the choice of scaling technique matters for classification performance, and the performance difference between the best and the worst scaling technique is relevant and statistically significant in most cases. They also indicate that choosing an inadequate technique can be more detrimental to classification performance than not scaling the data at all. We also show how the performance variation of an ensemble model, considering different scaling techniques, tends to be dictated by that of its base model. Finally, we discuss the relationship between a model's sensitivity to the choice of scaling technique and its performance and provide insights into its applicability on different model deployment scenarios. Full results and source code for the experiments in this paper are available in a GitHub repository.\footnote{https://github.com/amorimlb/scaling\_matters}

As an important data selection schema, active learning emerges as the essential component when iterating an Artificial Intelligence (AI) model. It becomes even more critical given the dominance of deep neural network based models, which are composed of a large number of parameters and data hungry, in application. Despite its indispensable role for developing AI models, research on active learning is not as intensive as other research directions. In this paper, we present a review of active learning through deep active learning approaches from the following perspectives: 1) technical advancements in active learning, 2) applications of active learning in computer vision, 3) industrial systems leveraging or with potential to leverage active learning for data iteration, 4) current limitations and future research directions. We expect this paper to clarify the significance of active learning in a modern AI model manufacturing process and to bring additional research attention to active learning. By addressing data automation challenges and coping with automated machine learning systems, active learning will facilitate democratization of AI technologies by boosting model production at scale.