Information Extraction versus Information Retrieval

Information extraction (IE) is unlike Information Retrieval (IR), which concerns how to identify relevant documents from a document collection, IE produces structured data ready for post-processing, which is crucial to many applications of Web mining and searching tools.

Programs that perform the task of IE are referred to as extractors or wrappers. A wrapper was originally defined as a component in an information integration system which aims at providing a single uniform query interface to access multiple information sources. In an information integration system, a wrapper is generally a program that “wraps” an information source (e.g. a database server, or a Web server) such that the information integration system can access that information source without changing its core query answering mechanism.