The MCAT math retrieval system for NTCIR-11 math track

This paper describes the participation of our MCAT search system in the NTCIR-11 Math-2 Task. The purpose of this task is to search mathematical expressions using hy-brid queries containing both formulae and keywords. We introduce an encoding technique to capture the structure and content of the mathematical expressions. Each expres-sion is accompanied by two types of automatically extracted textual information, namely words in context window and descriptions. In addition, we examine the improvement in ranking obtained by utilizing dependency graph of math-ematical expressions and post-retrieval reranking method. The results show that the use of description and depen-dency graph together delivers better ranking performances than the use of context window. Furthermore, using both the description and context window together delivers even better results. The evaluation results also indicate that our reranking method is effective for improving the ranking per-formances