Here's my understanding of the various environmental variables that
can be passed with a request, and exactly how they relate to the
actual URL:

WK_ABSOLUTE:
  if set, then the URL should be constructed by joining DOCUMENT_ROOT and REQUEST_URI (without query string, of course)
SCRIPT_NAME:
  points to the adapter portion of the URL (after rewrite)
PATH_INFO:
  the rest of the path after the adapter (after rewrite)
REQUEST_URI:
  the original URL requested (pre-rewrite ?)
REQUEST_FILENAME:
  the file the original URL would have pointed to (?) -- or maybe just a different name for SCRIPT_NAME
SCRIPT_URL:
  the path of the original (pre-rewrite) request
SCRIPT_URI:
  the full URI (with hostname) of the original (pre-rewrite) request

Information produced from this:

context:
  the context of the request
servlet:
  the servlet it points to
extraPathInfo:
  the extra portion of the URL
adapterURL:
  the url of the adapter
hostname:
  the hostname
servletURL:
  the url of the servlet, with adapter and context
fullURL:
  the url of the servlet, with extraPathInfo_ as well
webkitBaseURL:
  the url of the adapter
contextBaseURL:
  the url of the context

-- IanBicking_ - 26 Jun 2002