Holographic Embeddings of Knowledge Graphs

Learning embeddings of entities and relations is an efficient and versatile method to perform machine learning on relational data such as knowledge graphs. In this work, we propose holographic embeddings (HolE) to learn compositional vector space representations of entire knowledge graphs. The proposed method is related to holographic models of associative memory in that it employs circular correlation to create compositional representations. By using correlation as the compositional operator HolE can capture rich interactions but simultaneously remains efficient to compute, easy to train, and scalable to very large datasets. In extensive experiments we show that holographic embeddings are able to outperform state-of-the-art methods for link prediction in knowledge graphs and relational learning benchmark datasets.Comment: To appear in AAAI-1

Clustered multidimensional scaling with Rulkov neurons

Copyright ©2016 IEICEWhen dealing with high-dimensional measurements that often show non-linear characteristics at multiple scales, a need for unbiased and robust classification and interpretation techniques has emerged. Here, we present a method for mapping high-dimensional data onto low-dimensional spaces, allowing for a fast visual interpretation of the data. Classical approaches of dimensionality reduction attempt to preserve the geometry of the data. They often fail to correctly grasp cluster structures, for instance in high-dimensional situations, where distances between data points tend to become more similar. In order to cope with this clustering problem, we propose to combine classical multi-dimensional scaling with data clustering based on self-organization processes in neural networks, where the goal is to amplify rather than preserve local cluster structures. We find that applying dimensionality reduction techniques to the output of neural network based clustering not only allows for a convenient visual inspection, but also leads to further insights into the intraand inter-cluster connectivity. We report on an implementation of the method with Rulkov-Hebbian-learning clustering and illustrate its suitability in comparison to traditional methods by means of an artificial dataset and a real world example

An energy-based model for neuro-symbolic reasoning on knowledge graphs

Machine learning on graph-structured data has recently become a major topic in industry and research, finding many exciting applications such as recommender systems and automated theorem proving. We propose an energy-based graph embedding algorithm to characterize industrial automation systems, integrating knowledge from different domains like industrial automation, communications and cybersecurity. By combining knowledge from multiple domains, the learned model is capable of making context-aware predictions regarding novel system events and can be used to evaluate the severity of anomalies that might be indicative of, e.g., cybersecurity breaches. The presented model is mappable to a biologically-inspired neural architecture, serving as a first bridge between graph embedding methods and neuromorphic computing - uncovering a promising edge application for this upcoming technology.Comment: Accepted for publication at the 20th IEEE International Conference on Machine Learning and Applications (ICMLA 2021

Making decisions based on context: models and applications in cognitive sciences and natural language processing

It is known that humans are capable of making decisions based on context and generalizing what they have learned. This dissertation considers two related problem areas and proposes different models that take context information into account. By including the context, the proposed models exhibit strong performance in each of the problem areas considered. The first problem area focuses on a context association task studied in cognitive science, which evaluates the ability of a learning agent to associate specific stimuli with an appropriate response in particular spatial contexts. Four neural circuit models are proposed to model how the stimulus and context information are processed to produce a response. The neural networks are trained by modifying the strength of neural connections (weights) using principles of Hebbian learning. Such learning is considered biologically plausible, in contrast to back propagation techniques that do not have a solid neurophysiological basis. A series of theoretical results for the neural circuit models are established, guaranteeing convergence to an optimal configuration when all the stimulus-context pairs are provided during training. Among all the models, a specific model based on ideas from recommender systems trained with a primal-dual update rule, achieves perfect performance in learning and generalizing the mapping from context-stimulus pairs to correct responses. The second problem area considered in the thesis focuses on clinical natural language processing (NLP). A particular application is the development of deep-learning models for analyzing radiology reports. Four NLP tasks are considered including anatomy named entity recognition, negation detection, incidental finding detection, and clinical concept extraction. A hierarchical Recurrent Neural Network (RNN) is proposed for anatomy named entity recognition, which is then used to produce a set of features for incidental finding detection of pulmonary nodules. A clinical context word embedding model is obtained, which is used with an RNN to model clinical concept extraction. Finally, feature-enriched RNN and transformer-based models with contextual word embedding are proposed for negation detection. All these models take the (clinical) context information into account. The models are evaluated on different datasets and are shown to achieve strong performance, largely outperforming the state-of-art