Or an information extraction system designed for a business domain might extract the names of companies, products, facilities, and financial figures associated with business activities. Information extraction techniques are especially useful when the desired information can only be identified by recognizing conceptual roles. In contrast, some types of information are defined by the role that an item plays in a larger context. But it is impossible to identify companies involved in a joint venture activity simply by searching for company names. IE systems typically use extraction patterns that represent specific linguistic contexts to recognize relevant information.
Prepositions are also important for many patterns because they often identify role relationships.
We have shown that recognizing different verb forms and prepositions can dramatically improve the accuracy of some classification terms. Area References ACM Transactions on Information Systems, Special Issue on Text Categorization, Vol.