how about using feature negotiation for rationalizing a robot class namespace
-*-*-*-*-*-*-*-*-*-*-*-*-
 draft-holtman-http-negotiation-03.txt
   (Transparent Content Negotiation in HTTP) 
ABSTRACT
 
        HTTP allows one to put multiple versions of the same
        information under a single URL.  Transparent content
        negotiation is a mechanism, layered on top of HTTP, for
        automatically selecting the best version when the URL is
        accessed.  This enables the smooth deployment of new web data
        formats and markup tags.
 
        Design goals for transparent content negotiation include: low
        overhead on the request message size, downwards compatibility,
        extensibility, enabling the rapid introduction of new areas of
        negotiation, scalability, low cost for minimal support, end
        user control, and good cacheability.
 
-*-*-*-*-*-*-*-*-
an HTTP request-header
  robots-class-list: "name and version"
could dereference the appropriate robot class namespace version of
/robots.txt
benefits for robot builders: multiple robot class lists could exist under
this class list namespace.
implementors would choose from various class lists to fit their needs.
one class list would be extensive, another simple.  one for search engines,
another for previewers.
benefit to the server: the request for a /robots.txt reveals a user-agent
as well as a robots-class-list for more valuable hit data.  running robots
would be identified by user-agent as well as robot-class-list.
 -john
_________________________________________________
This messages was sent by the robots mailing list. To unsubscribe, send mail
to robots-request@webcrawler.com with the word "unsubscribe" in the body.
For more info see http://info.webcrawler.com/mak/projects/robots/robots.html