N-gram Index Structure Study for Semantic Based Mathematical Formula

Recently mathematical formula retrieval has become a hot and difficult problem in the field of information science research. The paper presents an N-grams division method of mathematical formula, determines the granularities of division by experiments, and proposes calculating method of a sub-formula weight based on the complexity of formula, the length of N-grams and depth. In addition, this paper considers the impact that operators made on weights of sub-formulas and gives a method of calculating the weight that sub-formula shares in the whole formula. Experiments show that the methods of N-grams division and index construction have great help for sub-formula matching and weighting computation. The methods can also improve the recall and precision of sub-formulas. The quick and feasible semantic based method can greatly enhance the semantic search capabilities of mathematical search.