Abstract Support Vector Machines (SVM) have been used successfully in many Natural Language Processing (NLP) tasks. The novel contribution of this paper is in investigating two techniques for making SVM more suitable for language learning tasks. Firstly, we propose an SVM with uneven margins (SVMUM) model to deal with the problem of imbalanced training data. Secondly, SVM active learning is employed in order to alleviate the difficulty in obtaining labelled training data. The algorithms are presented and evaluated on several Information Extraction (IE) tasks, where they achieved better performance than the standard SVM and the SVM with passive learning, respectively. Moreover, by combining SVMUM with the active learning algorithm, we achieve the best reported results on the seminars and jobs corpora, which are benchmark data sets used for evaluation and comparison of machine learning algorithms for IE. In addition, we also evaluate the token based classification framework for IE with three different entity tagging schemes. In comparison to previous methods dealing with the same problems, our methods are both effective and efficient, which are valuable features for real-world applications. Due to the similarity in the formulation of the learning problem for IE and for other NLP tasks, the two techniques are likely to be beneficial in a wide range of applications1.

Support Vector Machines (SVM) have obtained state-of-the-art results on many applications including document classification. However, previous works on applying SVMs to the F-term patent classification task did not obtain as good results as other learning algorithms such as kNN. This is due to the fact that F-term patent classification is different from conventional document classification in several aspects, mainly because it is a multiclass, multilabel classification problem with semi-structured documents and multi-faceted hierarchical categories. This article describes our SVM-based system and several techniques we developed successfully to adapt SVM for the specific features of the F-term patent classification task. We evaluate the techniques using the NTCIR-6 F-term classification terms assigned to Japanese patents. Moreover, our system participated in the NTCIR-6 patent classification evaluation and obtained the best results according to two of the three metrics used for task performance evaluation. Following the NTCIR-6 participation, we developed two new techniques, which achieved even better scores using all three NTCIR-6 metrics, effectively outperforming all participating systems. This article presents this new work and the experimental results that demonstrate the benefits of the latest approach.

Recent work on ontology-based Information Extraction (IE) has tried to make use of knowledge from the target ontology in order to improve semantic annotation results. However, very few approaches exploit the ontology structure itself, and those that do so, have some limitations. This paper introduces a hierarchical learning approach for IE, which uses the target ontology as an essential part of the extraction process, by taking into account the relations between concepts. The approach is evaluated on the largest available semantically annotated corpus. The results demonstrate clearly the benefits of using knowledge from the ontology as input to the information extraction process. We also demonstrate the advantages of our approach over other state-of-the-art learning systems on a commonly used benchmark dataset.