Performance Evaluation for Question Classification by Tree Kernels using Support Vector Machines

Question answering systems use information retrieval (IR) and information extraction (IE) methods to retrieve documents containing a valid answer. Question classification plays an important role in the question answer frame to reduce the gap between question and answer. This paper presents our research work on automatic question classification through machine learning approaches. We have experimented with machine learning algorithms Support Vector Machines (SVM) using kernel methods. An effective way to integrate syntactic structures for question classification in machine learning algorithms is the use of tree kernel (TK) functions. Here we use SubTree kernel, SubSet Tree kernel with Bag of words and Partial Tree kernels. Trade-off between training error and margin, Costfactor and the decay factor has significant impact when we use SVM for the above mentioned kernel types. The experiments determined the individual impact for Trade-off between training error and margin, Cost-factor and the decay factor and later the combined effect for Trade-off between training error and margin, Cost-factor. For each kernel types depending on these result we also figure out some hyper planes which can maximize the performance. Based on some standard data set outcomes of our experiment for question classification is promising. Index Terms — Precision, Recall, kernel, SubSet Tree, SubTree, Partial Tree, SVM, Question Classification, Question Answering.