Since PICS seems to be getting favorable comment in the CDA lawsuit, and it has cypherpunks relevance, I thought I would post some its most relevant features. From http://www.w3.org/pub/WWW/PICS/iacwc.htm
Labels can include two optional security features. The first is a message integrity check on the content of the resource that is labeled, in the form of an MD5 message digest... The second is a digital signature on the contents of the label itself...
... PICS specifies three ways to distribute labels. The first is to embed labels in HTML documents. This method will be helpful for those who wish to label content they have created.
The second method is for a client to ask an http server to send labels along with the documents it requests. The server would most likely offer the publishers' labels, but a server could also redistribute labels from third parties that it cooperates with. [Client sends URL of label service to browser which responds with that service's label. bf]
The third way to distribute labels is through a label bureau that dispenses only labels. A bureau could distribute labels created by one or more labeling services. A client asks the bureau for certain services' labels of specific resources. This is most likely to be used for third-party labels.
... PICS-compatible software can implement selective blocking features in various ways. ...[In] a browser ...On each computer, as part of the network protocol stack. ... Somewhere in the network, for example at a proxy server used in combination with a firewall. ...
PICS specifies very little about how to run a labeling service, beyond the format of the service description and the labels. Services can provide simple permission/prohibition labels, or provide information about any dimensions that they choose, from sex to coolness to literary quality. ... Third party labelers are likely to use a wide range of other dimensions. ... An interesting intermediate offering may be to label the resources that subscribers ask about: while there are thousands of sites and millions of resources available on the Internet, any particular set of users is likely to ask for access to a much smaller set. This approach could be particularly effective for a cooperative service formed by a number of like-minded parents or teachers.
While the primary goal of PICS is to facilitate the use of labels by selection software, PICS-compatible labels can also be used in other ways. For example, a labeling service might rate based on quality or classify resources by subject, ... Browsers could incorporate the contents of labels into visual displays that aid browsing, perhaps highlighting in green links to particularly popular or high-quality items or striking a red line through links to resources that are not recommended. It has even been suggested that labels could convey copyright ownership, distribution rights, and requested payments. Software could check for such labels and demand payment before distributing the labeled items.
One particularly promising application is collaborative filtering, where everyone can contribute ratings, and those ratings are used to guide others toward interesting materials. Guidance can be personalized by matching end-users with others who have similar tastes, as reflected in their ratings of resources that both have examined. A browser add-in feature would enable end-users to submit PICS rating labels to a labeling service.
Obviously, to get the full benefit of the technology, we will need more sophisticated browser support than just "access denied". If you contract with an outside service, one question to ask is, "Are you logging my accesses?" ------------------------------------------------------------------------ Bill Frantz | The CDA means | Periwinkle -- Computer Consulting (408)356-8506 | lost jobs and | 16345 Englewood Ave. frantz@netcom.com | dead teenagers | Los Gatos, CA 95032, USA