O'Reilly logo

Web Security and Commerce by Gene Spafford, Simson Garfinkel

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

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 "1996.6.01T00:01-0500" 
  until "1996.12.31T23:59-0500" 
  for "http://www.missionimpossible.com/" 
  by "Simson L. Garfinkel" 
  ratings (r 0))

This label describes the web site for the Paramont movie Mission: Impossible using the fictitious labeling service described in the previous section. The label was created on June 1, 1996, and is valid until December 31, 1996. 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 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 above label could be transmitted like this:

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

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required