The Platform for Internet Content Selection (PICS) is a World Wide Web Consortium ( W3C ) group that defines rating systems and rating information for Web-based content. The term also refers to a set of specifications developed by that group. PICS ratings give parents and teachers standards to help them decide what their children or students should be allowed to access on the Internet . The criteria can also be used for other purposes such as code signing and privacy assurance.
PICS labels are most often used in content filtering to block access to specific Web site s or page s based on labels associated with them. The system of labels works in much the same way as the labels used to define movies. The development of labels always involves subjective judgment because human beings must be involved at some point in the process to ensure that the labels are based on common sense. For example, a recipe for chicken breast with butter sauce should be all right for a child to read but might be flagged by a program that blindly labels content based on the presence of certain words alone. Human observation is also necessary in order to evaluate images that Web sites contain.
Independent companies called raters can provide content rating based on a set of words, phrases and character sequences called a vocabulary. This vocabulary is sophisticated enough to pass content that most people would consider acceptable while blocking content that most people would regard as objectionable. The paradigm resembles spam filter ing. The rater distributes the labels through a server known as a label bureau. When a computer is used in an attempt to access an Internet site, a program installed in that computer causes it to check at the label bureau before allowing or blocking the content. This slows down the connection speed as experienced by the user. Most concerned parents and teachers regard this as a negligible price to pay if the content filter functions properly.