Abstract: Recently, question and answering systems have attracted lots of attention. Given a question, the goal of question and answering is to return a concise, exact answer. According to the format of data, question and answering can be di-vided into three categories: the structural data based question and answering, the free-text based question and answering, the question-answer pairs based question and answering. This paper describes and summarizes the char-acteristics and related researches of these three categories respectively. Then, it discusses the future work of question and answering.

Key words: question and answering (QA), traditional question and answering (TQA), community-based question and an-swering (CQA), information retrieval, answer extraction

摘要： 近年来, 问答系统被大量广泛地研究。问答系统的目标是给定一个问题, 能够得到简短、精确的答案。根据处理数据的不同, 将问答系统分为三类：基于结构化数据的问答系统、基于自由文本的问答系统、基于问题答案对的问答系统。对这三大类系统的特点、面临的问题和相关的研究分别进行了叙述和总结。最后, 讨论了问答系统未来可能的研究方向。

关键词: 问答系统(QA), 传统问答系统(TQA), 基于社区的问答系统(CQA), 信息检索, 答案抽取