Information in a Web portal often is an integration of data collected from multiple sources. A typical example is the concept of one-stop service, for example, a single health portal provides a patient all of her/his health history, doctor’s information, test results, appointment bookings, insurance, and health reports. This concept involves information sharing among multiple parties, for example, hospital, drug store, and insurance company. On the other hand, the general public, however, has growing concerns about the use of personal information. Samarati (2001) shows that linking two data sources may lead to unexpectedly revealing sensitive information of individuals. In response, new privacy acts are enforced in many countries. For example, Canada launched the Personal Information Protection and Electronic Document Act in 2001 to protect a wide spectrum of information (The House of Commons in Canada, 2000). Consequently, companies cannot indiscriminately share their private information with other parties.