If you are going to add variable substitution to URL's, then perhaps
it would be best to define two types of variables: those which are
to be interpreted by the client, and those which the server should
expand.
Thus, a user could configure their browser session so as to
force a particular interpretation of any "variant" links
encountered. The $standardsite variable mentioned above is
one example of a variable which should be interpreted locally,
i.e. by the client.
Server-interpreted variables, on the other hand, could be used
by information administrators to ease the task of maintaining
document archives and to enhance reliability and efficiency. The
$parentsite and $parentdir variables mentioned in Jay's message
are examples of these types of variables. Another example would
be a $least_busy_server_of_group_GROUP variable, as in
http://$least_busy_of_group_GROUP/foo.html.
The server would replace this variable with the address of the least
busy server in the group of servers named GROUP.
So, how are the two types distinguished? Suppose that a server
variable is preceeded by a single '$'. and client variables would be
referenced by two $, o