Investigation and application of extension data mining based on rough set

In the database of information system, usually there are some attributes which are unimportant to the decision attribute, and some records that disturb the decision making. In this paper, reducing the condition attributes based on the matter-element theory and rough set method, calculating the importance to the decision attribute for each condition attribute after reduction, and data mining the relevant rules based on the reduced attributes, extension relevant function is used to depict quality of data gather in data mining. Finally, how to tap new customers and how to recommend an appropriate brand to new customers, Research result indicates that extension data mining can provide effective decide support for the decision-making of enterprise.