ABSTRACT
ABSTRACT: Question Answering Systems (QAS) are a unique kind of information retrieval. In Question Answering (QA) the system retrieves the precise answer to the questions asked by the user in natural language. QA is multidisciplinary. It involves information retrieval, natural language processing, linguistics, knowledge representation, databases, software engineering, artificial intelligence and so on. This paper classifies QAS based on different techniques used in answer ranking and answer extraction. The survey also provides the main contributions, experimental results, and limitations of various approaches. Finally, we discuss our perspective on the future direction of QAS.
