Cao, Caleb Chen
Towards Fine-Grained Explainability for Heterogeneous Graph Neural Network
Li, Tong, Deng, Jiale, Shen, Yanyan, Qiu, Luyu, Huang, Yongxiang, Cao, Caleb Chen
Recently, Their goal is to learn or search for optimal graph objects that heterogeneous graph neural networks (HGNs) have maximize mutual information with the predictions. While become one of the standard paradigms for modeling rich such explanations answer the question "what is salient to semantics of heterogeneous graphs in various application the prediction", they fail to unveil "how the salient objects domains such as e-commerce, finance, and healthcare (Lv affect the prediction". In particular, there may exist multiple et al. 2021; Wang et al. 2022). In parallel with the proliferation paths in the graph to propagate the information of the salient of HGNs, understanding the reasons behind the objects to the target object and affect its prediction. Without predictions from HGNs is urgently demanded in order to distinguishing these different influential paths, the answer to build trust and confidence in the models for both users and the "how" question remains unclear, which could compromise stakeholders. For example, a customer would be satisfied if the utility of the explanation. This issue becomes more an HGN-based recommender system accompanies recommended prominent when it comes to explaining HGNs due to the items with explanations; a bank manager may want complex semantics of heterogeneous graphs.
Model Debiasing via Gradient-based Explanation on Representation
Zhang, Jindi, Wang, Luning, Su, Dan, Huang, Yongxiang, Cao, Caleb Chen, Chen, Lei
Machine learning systems produce biased results towards certain demographic groups, known as the fairness problem. Recent approaches to tackle this problem learn a latent code (i.e., representation) through disentangled representation learning and then discard the latent code dimensions correlated with sensitive attributes (e.g., gender). Nevertheless, these approaches may suffer from incomplete disentanglement and overlook proxy attributes (proxies for sensitive attributes) when processing real-world data, especially for unstructured data, causing performance degradation in fairness and loss of useful information for downstream tasks. In this paper, we propose a novel fairness framework that performs debiasing with regard to both sensitive attributes and proxy attributes, which boosts the prediction performance of downstream task models without complete disentanglement. The main idea is to, first, leverage gradient-based explanation to find two model focuses, 1) one focus for predicting sensitive attributes and 2) the other focus for predicting downstream task labels, and second, use them to perturb the latent code that guides the training of downstream task models towards fairness and utility goals. We show empirically that our framework works with both disentangled and non-disentangled representation learning methods and achieves better fairness-accuracy trade-off on unstructured and structured datasets than previous state-of-the-art approaches.
ViT-CX: Causal Explanation of Vision Transformers
Xie, Weiyan, Li, Xiao-Hui, Cao, Caleb Chen, Zhang, Nevin L.
Despite the popularity of Vision Transformers (ViTs) and eXplainable AI (XAI), only a few explanation methods have been designed specially for ViTs thus far. They mostly use attention weights of the [CLS] token on patch embeddings and often produce unsatisfactory saliency maps. This paper proposes a novel method for explaining ViTs called ViT-CX. It is based on patch embeddings, rather than attentions paid to them, and their causal impacts on the model output. Other characteristics of ViTs such as causal overdetermination are also considered in the design of ViT-CX. The empirical results show that ViT-CX produces more meaningful saliency maps and does a better job revealing all important evidence for the predictions than previous methods. The explanation generated by ViT-CX also shows significantly better faithfulness to the model. The codes and appendix are available at https://github.com/vaynexie/CausalX-ViT.
Contrastive Domain Generalization via Logit Attribution Matching
Gao, Han, Li, Kaican, Huang, Yongxiang, Wang, Luning, Cao, Caleb Chen, Zhang, Nevin L.
Domain Generalization (DG) is an important open problem in machine learning. Deep models are susceptible to domain shifts of even minute degrees, which severely compromises their reliability in real applications. To alleviate the issue, most existing methods enforce various invariant constraints across multiple training domains. However,such an approach provides little performance guarantee for novel test domains in general. In this paper, we investigate a different approach named Contrastive Domain Generalization (CDG), which exploits semantic invariance exhibited by strongly contrastive data pairs in lieu of multiple domains. We present a causal DG theory that shows the potential capability of CDG; together with a regularization technique, Logit Attribution Matching (LAM), for realizing CDG. We empirically show that LAM outperforms state-of-the-art DG methods with only a small portion of paired data and that LAM helps models better focus on semantic features which are crucial to DG.
Towards Efficient Visual Simplification of Computational Graphs in Deep Neural Networks
Pan, Rusheng, Wang, Zhiyong, Wei, Yating, Gao, Han, Ou, Gongchang, Cao, Caleb Chen, Xu, Jingli, Xu, Tong, Chen, Wei
A computational graph in a deep neural network (DNN) denotes a specific data flow diagram (DFD) composed of many tensors and operators. Existing toolkits for visualizing computational graphs are not applicable when the structure is highly complicated and large-scale (e.g., BERT [1]). To address this problem, we propose leveraging a suite of visual simplification techniques, including a cycle-removing method, a module-based edge-pruning algorithm, and an isomorphic subgraph stacking strategy. We design and implement an interactive visualization system that is suitable for computational graphs with up to 10 thousand elements. Experimental results and usage scenarios demonstrate that our tool reduces 60% elements on average and hence enhances the performance for recognizing and diagnosing DNN models. Our contributions are integrated into an open-source DNN visualization toolkit, namely, MindInsight [2].
TDLS: A Top-Down Layer Searching Algorithm for Generating Counterfactual Visual Explanation
Wang, Cong, Han, Haocheng, Cao, Caleb Chen
Explanation of AI, as well as fairness of algorithms' decisions and the transparency of the decision model, are becoming more and more important. And it is crucial to design effective and human-friendly techniques when opening the black-box model. Counterfactual conforms to the human way of thinking and provides a human-friendly explanation, and its corresponding explanation algorithm refers to a strategic alternation of a given data point so that its model output is "counter-facted", i.e. the prediction is reverted. In this paper, we adapt counterfactual explanation over fine-grained image classification problem. We demonstrated an adaptive method that could give a counterfactual explanation by showing the composed counterfactual feature map using top-down layer searching algorithm (TDLS). We have proved that our TDLS algorithm could provide more flexible counterfactual visual explanation in an efficient way using VGG-16 model on Caltech-UCSD Birds 200 dataset. At the end, we discussed several applicable scenarios of counterfactual visual explanations.
Resisting Out-of-Distribution Data Problem in Perturbation of XAI
Qiu, Luyu, Yang, Yi, Cao, Caleb Chen, Liu, Jing, Zheng, Yueyuan, Ngai, Hilary Hei Ting, Hsiao, Janet, Chen, Lei
With the rapid development of eXplainable Artificial Intelligence (XAI), perturbation-based XAI algorithms have become quite popular due to their effectiveness and ease of implementation. The vast majority of perturbation-based XAI techniques face the challenge of Out-of-Distribution (OoD) data -- an artifact of randomly perturbed data becoming inconsistent with the original dataset. OoD data leads to the over-confidence problem in model predictions, making the existing XAI approaches unreliable. To our best knowledge, the OoD data problem in perturbation-based XAI algorithms has not been adequately addressed in the literature. In this work, we address this OoD data problem by designing an additional module quantifying the affinity between the perturbed data and the original dataset distribution, which is integrated into the process of aggregation. Our solution is shown to be compatible with the most popular perturbation-based XAI algorithms, such as RISE, OCCLUSION, and LIME. Experiments have confirmed that our methods demonstrate a significant improvement in general cases using both computational and cognitive metrics. Especially in the case of degradation, our proposed approach demonstrates outstanding performance comparing to baselines. Besides, our solution also resolves a fundamental problem with the faithfulness indicator, a commonly used evaluation metric of XAI algorithms that appears to be sensitive to the OoD issue.
Quantitative Evaluations on Saliency Methods: An Experimental Study
Li, Xiao-Hui, Shi, Yuhan, Li, Haoyang, Bai, Wei, Song, Yuanwei, Cao, Caleb Chen, Chen, Lei
It has been long debated that eXplainable AI (XAI) is an important topic, but it lacks rigorous definition and fair metrics. In this paper, we briefly summarize the status quo of the metrics, along with an exhaustive experimental study based on them, including faithfulness, localization, false-positives, sensitivity check, and stability. With the experimental results, we conclude that among all the methods we compare, no single explanation method dominates others in all metrics. Nonetheless, Gradient-weighted Class Activation Mapping (Grad-CAM) and Randomly Input Sampling for Explanation (RISE) perform fairly well in most of the metrics. Utilizing a set of filtered metrics, we further present a case study to diagnose the classification bases for models. While providing a comprehensive experimental study of metrics, we also examine measuring factors that are missed in current metrics and hope this valuable work could serve as a guide for future research.