Madhav Nimishakavi

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  • Event Schema Induction using Tensor Factorization with Back-off

    The goal of Event Schema Induction(ESI) is to identify schemas of events from a corpus of documents. For example, given documents from the sports domain, we would like to infer that win(WinningPlayer, Trophy, OpponentPlayer, Location) is an important event schema for this domain. Automatic discovery of such event schemas is an important first step towards building domain-specific Knowledge Graphs (KGs). ESI has been the focus of some prior research, with generative models achieving the best performance. In this paper,we propose TFB, a tensor factorization-based method with back-off for ESI. TFB solves a novel objective to factorize Open Information Extraction (OpenIE) tuples for inducing binary schemas. Event schemas are induced out of this set of binary schemas by solving a constrained clique problem. To the best of our knowledge this is the first application of tensor factorization for the ESI problem. TFB outperforms current state-of-the-art by 52 (absolute) points gain in accuracy, while achieving 90x speedup on average. We hope to make all the code and datasets used in the paper publicly available upon publication of the paper.

    07/06/2017 ∙ by Madhav Nimishakavi, et al. ∙ 0 share

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  • Relation Schema Induction using Tensor Factorization with Side Information

    Given a set of documents from a specific domain (e.g., medical research journals), how do we automatically build a Knowledge Graph (KG) for that domain? Automatic identification of relations and their schemas, i.e., type signature of arguments of relations (e.g., undergo(Patient, Surgery)), is an important first step towards this goal. We refer to this problem as Relation Schema Induction (RSI). In this paper, we propose Schema Induction using Coupled Tensor Factorization (SICTF), a novel tensor factorization method for relation schema induction. SICTF factorizes Open Information Extraction (OpenIE) triples extracted from a domain corpus along with additional side information in a principled way to induce relation schemas. To the best of our knowledge, this is the first application of tensor factorization for the RSI problem. Through extensive experiments on multiple real-world datasets, we find that SICTF is not only more accurate than state-of-the-art baselines, but also significantly faster (about 14x faster).

    05/12/2016 ∙ by Madhav Nimishakavi, et al. ∙ 0 share

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  • A Dual Framework for Low-rank Tensor Completion

    We propose a novel formulation of the low-rank tensor completion problem that is based on the duality theory and a particular choice of low-rank regularizer. This low-rank regularizer along with the dual perspective provides a simple characterization of the solution to the tensor completion problem. Motivated by large-scale setting, we next derive a rank-constrained reformulation of the proposed optimization problem, which is shown to lie on the Riemannian spectrahedron manifold. We exploit the versatile Riemannian optimization framework to develop computationally efficient conjugate gradient and trust-region algorithms. The experiments confirm the benefits of our choice of regularization and the proposed algorithms outperform state-of-the-art algorithms on several real-world data sets in different applications.

    12/04/2017 ∙ by Madhav Nimishakavi, et al. ∙ 0 share

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  • Inductive Framework for Multi-Aspect Streaming Tensor Completion with Side Information

    Low-rank tensor completion is a well-studied problem and has applications in various fields. However, in many real-world applications the data is dynamic, i.e., the tensor grows as new data arrives. Besides the tensor, in many real-world scenarios, side information is also available in the form of matrices which also grow. Existing work on dynamic tensor completion do not incorporate side information and most of the previous work is based on the assumption that the tensor grows only in one mode. We bridge this gap in this paper by proposing a dynamic tensor completion framework called Side Information infused Incremental Tensor Analysis (SIITA), which incorporates side information and works for general incremental tensors. We carry out extensive experiments on multiple real-world datasets to demonstrate the effectiveness of SIITA in various different settings.

    02/18/2018 ∙ by Madhav Nimishakavi, et al. ∙ 0 share

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  • Lovasz Convolutional Networks

    Semi-supervised learning on graph structured data has received significant attention with the recent introduction of graph convolution networks (GCN). While traditional methods have focused on optimizing a loss augmented with Laplacian regularization framework, GCNs perform an implicit Laplacian type regularization to capture local graph structure. In this work, we propose Lovasz convolutional network (LCNs) which are capable of incorporating global graph properties. LCNs achieve this by utilizing Lovasz's orthonormal embeddings of the nodes. We analyse local and global properties of graphs and demonstrate settings where LCNs tend to work better than GCNs. We validate the proposed method on standard random graph models such as stochastic block models (SBM) and certain community structure based graphs where LCNs outperform GCNs and learn more intuitive embeddings. We also perform extensive binary and multi-class classification experiments on real world datasets to demonstrate LCN's effectiveness. In addition to simple graphs, we also demonstrate the use of LCNs on hypergraphs by identifying settings where they are expected to work better than GCNs.

    05/29/2018 ∙ by Prateek Yadav, et al. ∙ 0 share

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  • HyperGCN: Hypergraph Convolutional Networks for Semi-Supervised Classification

    Graph-based semi-supervised learning (SSL) is an important learning problem where the goal is to assign labels to initially unlabeled nodes in a graph. Graph Convolutional Networks (GCNs) have recently been shown to be effective for graph-based SSL problems. GCNs inherently assume existence of pairwise relationships in the graph-structured data. However, in many real-world problems, relationships go beyond pairwise connections and hence are more complex. Hypergraphs provide a natural modeling tool to capture such complex relationships. In this work, we explore the use of GCNs for hypergraph-based SSL. In particular, we propose HyperGCN, an SSL method which uses a layer-wise propagation rule for convolutional neural networks operating directly on hypergraphs. To the best of our knowledge, this is the first principled adaptation of GCNs to hypergraphs. HyperGCN is able to encode both the hypergraph structure and hypernode features in an effective manner. Through detailed experimentation, we demonstrate HyperGCN's effectiveness at hypergraph-based SSL.

    09/07/2018 ∙ by Naganand Yadati, et al. ∙ 0 share

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