1. Multi-view Exploratory Learning for AKBC Problems Bhavana Dalvi and William W. Cohen School Of Computer Science, Carnegie Mellon University Motivation Modeling Unobserved Classes Multi-view Exploratory EM AKBC tasks Acknowledgements : This work is supported by Google PhD Fellowship in Information Extraction and a Google Research Grant. Conclusions  Traditional EM method for SSL jointly learns missing labels of unlabeled data points as well as model parameters.  We consider two extensions of traditional EM for SSL:  We consider a new latent variable, unobserved classes, by dynamically introducing new classes when appropriate.  Assigning multiple labels from multiple levels of class hierarchy while satisfying ontological constraints, and considering multiple data views.  Our proposed framework combines structural search for the best class hierarchy with SSL, reducing the semantic draft associated with erroneously grouping unanticipated classes with expected classes.  Exploratory learning helps reduce semantic drift of seeded classes. It gets more powerful in conjunction with multiple data views and class hierarchy, when imposed as soft-constraints on the label vectors.  It can be applied for multiple AKBC tasks like macro- reading, gloss finding, ontology extension etc.  Datasets and code can be downloaded from: www.cs.cmu.edu/~bbd/exploratory_learning Model Selection  This step makes sure that we do not create too many new classes.  We tried BIC, AIC, and AICc criteria, and Extended AIC (AICc) worked best for our tasks. AICc(g) = AIC(g) + 2 * v * (v+1) / (n – v -1) Here g: Model being evaluated, L(g): Log-likelihood of data given g, v: Number of free parameters of the model, n: Number of data points. Multiple Data Views Incorporating Multiple Views and Ontological Constraints  Each data point is assigned a bit vector of labels. Subset and mutual exclusion constraints decide consistency of potential bit vectors.  GLOFIN: A mixed integer program is solved for each data point to get optimal label vector. [Dalvi et al. WSDM 2015]  Optimized Divide and Conquer (OptDAC): Here we combine 1) divide and conquer based top-down strategy to detect and place new categories in the ontology, with 2) mixed integer programming technique (GLOFIN) to select optimal set of labels for a data point, consistent w.r.t. ontological constraints.  Semi-supervised classification of noun-phrases into categories, using distributional features.  Exploratory learning can reduce semantic drift of seed classes. [Dalvi et al. ECML 2013] Macro-reading (Explore-EM) Micro-reading  Task: To classify an entity mention using context specific features.  Clustering NIL entities for KBP entity discovery and linking (EDL) task [Mazaitis et al., KBP 2014] Multi-view Hierarchical SSL (MaxAgree)  MaxAgree method exploits clues from different data views.  We define multi-view clustering as an optimization problem and compare various methods for combining scores across views. MaxAgree method is more robust compared to Prod-Score method when we vary difference of performance between views.  Our proposed Hier-MaxAgree method can incorporate both: the clues from multiple view, and ontological constraints. [Dalvi and Cohen, in submission]  On entity classification for NELL KB, our proposed Hier-MaxAgree method gave state-of-the-art performance. Different Document Representations  Naïve Bayes: Assumes multinomial distribution for feature occurrences, explicitly models class prior.  Seeded K-Means: Similarity based on cosine distance between centroids and data points  Seeded von Mises-Fisher: SSL method for data distributed on the unit hyper-sphere. Ontological Constraints Automatic gloss finding for KBs (GLOFIN)  We developed GLOFIN method that takes a gloss-free KB, a large collection of glosses and automatically matches glosses to entities in the KB. [Dalvi et al. WSDM 2015]  We used Glosses with only one candidate KB entity (unambiguous glosses) are used as training data to train hierarchical classification model for categories in the KB. Ambiguous glosses are then disambiguated based on the KB category they are put in.  Our method outperformed SVM and a label propagation baseline especially when amount of training data is small.  In future: Apply GLOFIN to word sense disambiguation w.r.t. WordNet synset hierarchy. Hierarchical Exploratory Learning (OptDAC)  We proposed OptDAC that can do hierarchical SSL in the presence of incomplete class ontologies.  It employs mixed integer programming formulation to find optimal label assignments for a data point, while traversing the class ontology in top- down fashion to detect whether a new class needs to be added and where to place it. [Dalvi and Cohen, under review] 1 2 34 5 6 Performance improvement over best view Correlation w.r.t difference in views CoefficientP-value Prod-Score-0.590.01 MaxAgree-0.050.82 Text-patterns + Ontology-1 Text-patterns + Ontology-2 HTML-tables + Ontology-1 HTML-tables + Ontology-2 An example of extended ontology by OptDAC Root Food Location Country State Vegetable Condiment 1.0 Coke 0.1 0.9 0.550.45 C8 Example use-case of Exploratory EM 20 Newsgroups Dataset (#seed classes = 6)