Open Information Extraction

The research on information extraction is being developed into open information extraction,i.e.extracting open categories of entities,relations and events from open domain text resources.The methods used are also transferred from pure statistical machine learning model based on human annotated corpora into statistical learning model incorporated with knowledge bases mined from large-scaled and heterogeneous Web resources.This paper firstly reviews the history of the researches on information extraction,then detailedly introduces the task definitions,difficulties,typical methods,evaluations,performances and the challenges of three main open domain information extraction tasks,i.e.entity extraction,entity disambiguation and relation extraction.Finally,based on our researches on this field,we analyze and discuss the development directions of open information extraction research and its applications in large-scaled knowledge engineering,question answering,etc.