In SDI service, the information in a library is matched against the subject interests of the users; which means that the user receives only that information which is relevant to his research work. In computerized SDI service, a user profile is constructed. Simultaneously, document profile is also constructed when documents are received in the library. Both these profiles are matched by the computer and sent to the user. Feedback is received from the user. In case the user is not satisfied then the profiles are checked and adjusted on the basis of user’s evaluation.