One important use for computer systems is data mining, in other words, discovering, and condensing information from various sources. During the information retrieval, data mining may be used to identify trends, to improve operating efficiency, and extract information from disparate sources, such as unstructured documents. Information extraction (IE) is a type of information retrieval whose goal is to automatically extract and structure information from unstructured documents. After extraction the information may be structured by being categorized and contextually and semantically well-defined. Thus, the information may be manipulated and managed as any other structured data.