Social networking services (SNSs) are regarded as an indispensable social media for finding friends and interacting with them. However, their search capabilities often raise privacy concerns. Usually, an SNS provides privacy settings for each user, so that he/she can specify who can access his/her online contents.
Wikipedia is well known as a free encyclopedia, which is a type of collaborative repository system that allows the viewer to create and edit articles directly in the web browser.
  Keyword retrieval exploits frequencies and positions of search keywords in target documents. As for retrieval by two or more keywords, semantic relation between keywords is important to improve accuracy.
When using web services, users are often requested to provide their identity attributes, such as name, age, mail address, phone number, social security number, as well as private attributes such as education, ethnicity, medical history, and marriage status. Users also have to manage their accounts on various web services.