For example, it could inform a blind visitor at a certain Web site that the content therein is entirely graphic, but that a text-only version, which can be read with a screen reader, can be found at another site. Metadata is employed in a technology called filtering, which allows users to set up parameters about the information that they want to receive or see. The recent implementations of filtering were born of the cyberporn controversy. Parental concerns about their children's access to nudity on the Net fueled a media blitz, which culminated in a cover story in Time in July 1995. The idea behind PICS is straightforward.
Web pages receive a label or tag that rates one or more attributes on a numeric scale.
PICS defines a universal notation that allows groups like RSAC to describe who they are and what content attributes they rate so that a PICS filter knows how to match the vocabulary of the label to the user's stated preferences. Users can also be told what they need to know to frame their preferences. In the case of RSAC, owners rate their own Web sites, but RSAC conducts random audits. It heavily fines owners of sites that it finds to be falsely labeled. Other PICS rating systems, such as Canada's Net Shepherd Inc., use independent reviewers to assign ratings, and stores them on its own servers.