1.Abstraction

　　several different techniques to answer extraction for factoid question answering

2.Introduction

types of question:

• definitional questions
• list questions
• scenario-based QA
• why-type questions

evaluation track of question answering systems:

• Text REtrieval Confererence(TREC)(Voorhees 2001,2003b)
• CLEF
• NTCIR(focus on European languages and Asia languages respectively)

why choose factoid questions?

• clear defined and relatively uncontroversial evaluation standards
• usually one or at most a few correct answers to given question
• the answer-a single word token or a short phrase
• the range in not very high,plenty of room for further improvement

Assessment classes of each factoid answer:

TREC&CLEF:

• correct
• correct+unsupported
• unsupported
• inxact(adj. 不确切的)
• incorrect

 Assessment scores of each factoid answer:

• top1 and top5 accuracies
• Mean Reciprocal Rank(MRR)