Web Security, Privacy & Commerce, 2nd Edition

PICS Labels

The PICS label specification defines the syntax for document labels. Labels can be obtained over the Web from a search service using an HTTP extension defined in the PICS standard. Alternatively, labels can be automatically included with a document, as part of the document’s header.

Here is a PICS label that ranks a URL using the service described in the previous section:

(PICS-1.0 "http://moviescale.org/v1.0" 
 labels 
  on "2002.6.01T00:01-0500" 
  until "2002.12.31T23:59-0500" 
  for "http://www.missionimpossible.com/" 
  by "Simson L. Garfinkel" 
  ratings (r 0))

This label describes the web site for the Paramount movie Mission: Impossible using the fictitious labeling service described in the previous section. The label was created on June 1, 2002, and is valid until December 31, 2002. The label is for information stored at the URL >http://www.missionimpossible.com/. The label was written by Simson L. Garfinkel. Finally, the label gives the rating “(r 0).”

Although the movie Mission: Impossible had a rating of “R,” the web site has a rating of “G.” (The value “G” is transmitted with 0 using the http://moviescale.org/v1.0 rating service.)

Ratings may include more than one transmitted value. For example, if a rating service defined two scales, a label rating might look like this: “(r 3 n 4).”

Labels can be substantially compressed by removing nearly all information except the ratings themselves. For example, the previous label could be transmitted like this:

(PICS-1.0 "http://moviescale.org/v1.0" ...