Platform for Internet Content Selection (PICS)
The PICS specification enables
labels (metadata) to be associated with Internet content. It was
originally designed to help parents and teachers control what children
access on the Internet, but it also facilitates other uses for labels,
including code signing and privacy. The PICS platform is one on which
other rating services and filtering software have been built.
The PICS system has two types of components: rating systems and rating
labels. A rating system defines the criteria for how content is rated.
The rating label is the actual rating information. The label can appear
on a Web page as part of the HTML content, on a third-party Web site,
or anywhere else that a particular client application "knows" to look
for them. Each item of content that is rated has its own label. PICS
has defined the syntax for these rating labels, as well as extensions
to many Internet protocols to support labels.
The PICS system works by matching labels to their associated systems.
In order to advance its goals, PICS will devise a set of standards that
facilitate the following:
The most important components are:
- Self-rating: enable content providers to voluntarily label the
content they create and distribute
- Third-party rating: enable multiple, independent labeling
services to associate additional labels with content created and
distributed by others. Services may devise their own labeling systems,
and the same content may receive different labels from different
- Ease-of-use: enable parents and teachers to use ratings and
labels from a diversity of sources to control the information that
children under their supervision receive.
Membership in PICS includes a broad cross-section of companies from the
computer, communications, and content industries, as well as trade
associations and public interest groups. PICS member will deploy
products and services based on these standards.
- A syntax for describing a rating service, so that computer
programs can present the service and its labels to users
- A syntax for labels, so that computer programs can process them.
A label describes either a single document or a group of documents
(e.g., a site.) A label may be digitally signed and may include a
cryptographic hash of the associated document
- An embedding of labels (actually, lists of labels) into the HTML
- An extension of the HTTP protocol, so clients can request that
labels be transmitted with a document
- A query-syntax for an on-line database of labels