查看更多>>摘要：Determining user geolocation from social media data is essential in various location-based applications - from improved transportation/supply management, through providing personalized services and targeted marketing, to better overall user experiences. Previous methods rely on the similarity of user posting content and neighboring nodes for user geolocation, which suffer the problems of: (1) position-agnostic of network representation learning, which impedes the performance of their prediction accuracy; and (2) noisy and unstable user relation fusion due to the flat graph embedding methods employed. This work presents Hierarchical Graph Neural Networks (HGNN) - a novel methodology for location-aware collaborative user -aspect data fusion and location prediction. It incorporates geographical location information of users and clustering effect of regions and can capture topological relations while preserving their relative positions. By encoding the structure and features of regions with hierarchical graph learning, HGNN can primarily alleviate the problem of noisy and unstable signal fusion. We further design a relation mechanism to bridge connections between individual users and clusters, which not only leverages the information of isolated nodes that are useless in previous methods but also captures the relations between unlabeled nodes and labeled subgraphs. Furthermore, we introduce a robust statistics method to interpret the behavior of our model by identifying the importance of data samples when predicting the locations of the users. It provides meaningful explanations on the model behaviors and outputs, overcoming the drawbacks of previous approaches that treat user geolocation as "black-box"modeling and lacking interpretability. Comprehensive evaluations on real-world Twitter datasets verify the proposed model's superior performance and its ability to interpret the user geolocation results.
查看更多>>摘要：The rise of deep learning in today's applications entailed an increasing need in explaining the model's decisions beyond prediction performances in order to foster trust and accountability. Recently, the field of explainable AI (XAI) has developed methods that provide such explanations for already trained neural networks. In computer vision tasks such explanations, termed heatmaps, visualize the contributions of individual pixels to the prediction. So far XAI methods along with their heatmaps were mainly validated qualitatively via human-based assessment, or evaluated through auxiliary proxy tasks such as pixel perturbation, weak object localization or randomization tests. Due to the lack of an objective and commonly accepted quality measure for heatmaps, it was debatable which XAI method performs best and whether explanations can be trusted at all. In the present work, we tackle the problem by proposing a ground truth based evaluation framework for XAI methods based on the CLEVR visual question answering task. Our framework provides a (1) selective, (2) controlled and (3) realistic testbed for the evaluation of neural network explanations. We compare ten different explanation methods, resulting in new insights about the quality and properties of XAI methods, sometimes contradicting with conclusions from previous comparative studies. The CLEVR-XAI dataset and the benchmarking code can be found at https://github.com/ahmedmagdiosman/clevr-xai.
查看更多>>摘要：Explanation abilities are required for data-driven models, where the high number of parameters may render its internal reasoning opaque to users. Despite the natural transparency brought by the graphical model structure of Bayesian networks, decisions trees or valuation networks, additional explanation abilities are still required due to both the complexity of the problem as well as the consequences of the decision to be taken. Threat assessment is an example of such a complex problem in which several sources with partially unknown behaviour provide information on distinct but related frames of discernment. In this paper, we propose a solution as an evidential network with explanation abilities to detect and investigate threat to maritime infrastructure. We propose a post-hoc explanation approach to an already transparent by design threat assessment model, combining feature relevance and natural language explanations with some visual support. To this end, we extend the sensitivity analysis method of generation of explanations for evidential reasoning to a multi-source model where sources can have several and disparate behaviours. Natural language explanations are generated on the basis of a series of sensitivity measures quantifying the impact of both direct reports and source models. We conclude on challenges to be addressed in future work.
查看更多>>摘要：Deep learning models have achieved high performance across different domains, such as medical decision making, autonomous vehicles, decision support systems, among many others. However, despite this success, the inner mechanisms of these models are opaque because their internal representations are too complex for a human to understand. This opacity makes it hard to understand the how or the why of the predictions of deep learning models. There has been a growing interest in model-agnostic methods that make deep learning models more transparent and explainable to humans. Some researchers recently argued that for a machine to achieve human level explainability, this machine needs to provide human causally understandable explanations, also known as causability. A specific class of algorithms that have the potential to provide causability are counterfactuals. This paper presents an in-depth systematic review of the diverse existing literature on counterfactuals and causability for explainable artificial intelligence (AI). We performed a Latent Dirichlet topic modelling analysis (LDA) under a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework to find the most relevant literature articles. This analysis yielded a novel taxonomy that considers the grounding theories of the surveyed algorithms, together with their underlying properties and applications to real-world data. Our research suggests that current model-agnostic counterfactual algorithms for explainable AI are not grounded on a causal theoretical formalism and, consequently, cannot promote causability to a human decision-maker. Furthermore, our findings suggest that the explanations derived from popular algorithms in the literature provide spurious correlations rather than cause/effects relationships, leading to sub-optimal, erroneous, or even biased explanations. Thus, this paper also advances the literature with new directions and challenges on promoting causability in model-agnostic approaches for explainable AI.
查看更多>>摘要：A key element in solving real-life data science problems is selecting the types of models to use. Tree ensemble models (such as XGBoost) are usually recommended for classification and regression problems with tabular data. However, several deep learning models for tabular data have recently been proposed, claiming to outperform XGBoost for some use cases. This paper explores whether these deep models should be a recommended option for tabular data by rigorously comparing the new deep models to XGBoost on various datasets. In addition to systematically comparing their performance, we consider the tuning and computation they require. Our study shows that XGBoost outperforms these deep models across the datasets, including the datasets used in the papers that proposed the deep models. We also demonstrate that XGBoost requires much less tuning. On the positive side, we show that an ensemble of deep models and XGBoost performs better on these datasets than XGBoost alone.
查看更多>>摘要：The paper proposes a novel architecture for explainable artificial intelligence based on semantic technologies and artificial intelligence. We tailor the architecture for the domain of demand forecasting and validate it on a real-world case study. The explanations provided result from knowledge fusion regarding concepts describing features relevant to a particular forecast, related media events, and metadata regarding external datasets of interest. The Knowledge Graph enhances the quality of explanations by informing concepts at a higher abstraction level rather than specific features. By doing so, explanations avoid exposing sensitive details regarding the demand forecasting models, thus preserving confidentiality. In addition, the Knowledge Graph enables linking domain knowledge, forecasted values, and forecast explanations while also providing insights into actionable aspects on which users can take action. The ontology and dataset we developed for this use case are publicly available for further research.
查看更多>>摘要：The need for explanations of ML systems is growing as new models outperform their predecessors while becoming more complex and less comprehensible for their end-users. Though several XAI methods have been proposed in recent years, not enough attention was paid to explaining how models change their behaviour in contrast with previous ones (e.g., due to retraining). In such cases, an XAI system should explain why the model changes its predictions concerning past outcomes. Capturing and understanding such differences is crucial, as the need for trust is key in any application to support human-AI decision-making processes. This is the idea of ContrXT, a novel approach that (i) traces the decision criteria of a black box text classifier by encoding the changes in the decision logic through Binary Decision Diagrams. Then (ii) it provides global, model-agnostic, Time-Contrastive (T-contrast) explanations in natural language, estimating why - and to what extent - the model has modified its behaviour over time. We implemented and evaluated ContrXT over several supervised ML models trained on a benchmark dataset and a real-life application, showing it is effective in catching majorly changed classes and in explaining their variation through a user study. The approach has been implemented, and it is available to the community both as a python package and through REST API, providing contrastive explanations as a service.
查看更多>>摘要：For reliability, it is important for the predictions made by machine learning methods to be interpretable by humans. In general, deep neural networks (DNNs) can provide accurate predictions, although it is difficult to interpret why such predictions are obtained by the DNNs. On the other hand, interpretation of linear models is easy, although their predictive performance is low because real-world data are often intrinsically non-linear. To combine both the benefits of the high predictive performance of DNNs and the high interpretability of linear models into a single model, we propose neural generators of sparse local linear models (NGSLL). Sparse local linear models have high flexibility because they can approximate non-linear functions. NGSLL generates sparse linear weights for each sample using DNNs that take the original representations of each sample (e.g., word sequence) and their simplified representations (e.g., bag-of-words) as input. By extracting features from the original representations, the weights can contain rich information and achieve a high predictive performance. In addition, the prediction is interpretable because it is obtained through the inner product between the simplified representations and the sparse weights, where only a small number of weights are selected by our gate module in NGSLL. In experiments on image, text and tabular datasets, we demonstrate the effectiveness of NGSLL quantitatively and qualitatively by evaluating the prediction performance and visualizing generated weights.
查看更多>>摘要：This paper addresses the intrinsic Cramer-Rao bounds (CRBs) for a distributed Bayesian estimator whose states and measurements are on Riemannian manifolds. As Euclidean-based CRBs for recursive Bayesian estimator are no longer applicable to general Riemannian manifolds, the bounds need redesigning to accommodate the non-zero Riemannian curvature. To derive the intrinsic CRBs, we append a coordination step to the recursive Bayesian procedure, where the proposed sequential steps are prediction, measurement and coordination updates. In the coordination step, the estimator minimises the Kullback-Liebler divergence to obtain the consensus of multiple probability density functions (PDFs). Employing the PDFs from those steps together with the affine connection on manifolds the Fisher Information Matrix (FIM) and the curvature terms of the corresponding intrinsic bounds are derived. Subsequently, the design of a distributed estimator for Riemannian information manifold with Gaussian distribution - referred to as distributed Riemannian Kalman filter - is also presented to exemplify the application of the proposed intrinsic bounds. Finally, simulations utilising the designed filter for a distributed quaternionic estimation problem verifies that the covariance matrices of the filter are never below the formulated intrinsic CRBs.
查看更多>>摘要：When it comes to complex machine learning models, commonly referred to as black boxes, understanding the underlying decision making process is crucial for domains such as healthcare and financial services, as well as when they are used in connection with safety critical systems such as autonomous vehicles. As a result, interest in explainable artificial intelligence (xAI) tools and techniques has increased in recent years. However, the user experience (UX) effectiveness of existing xAI frameworks, especially concerning algorithms that work with data as opposed to images, is still an open research question. In order to address this gap, we examine the UX effectiveness of the Local Interpretable Model-Agnostic Explanations (LIME) xAI framework, one of the most popular model agnostic frameworks found in the literature, with a specific focus on its performance in terms of making tabular models more interpretable. In particular, we apply several state of the art machine learning algorithms on a tabular dataset, and demonstrate how LIME can be used to supplement conventional performance assessment methods. Based on this experience, we evaluate the understandability of the output produced by LIME both via a usability study, involving participants who are not familiar with LIME, and its overall usability via a custom made assessment framework, called Model Usability Evaluation (MUsE), which is derived from the International Organisation for Standardisation 9241-11:2018 standard.
NSTL
Elsevier