This is a comma-delimited list of system Resources and associated
permissions. A user must hold the specified permissions on at least
one of the specified resources in order to view this page or
invoke any of its server-side methods from the client.
The format of each item in the list should be as follows:
Resource[:Permission]
Permission is optional, and defaults to USE if not supplied. If it
is supplied, it should be one of USE, READ or WRITE.
Zen page notification of an HTTP request. This method can be overwritten
by subclasses.
This is called before the standard Zen pre-HTTP processing occurs.