ltl2tgba.html is a dynamic web page that translates user-supplied LTL
formulae to Transition-based Generalized Büchi Automata.  The actual
translation work is performed by a CGI script in Python: spotcgi.py.

There are two ways to use the script: using a web server such as
Apache, or standalone.

In both cases you should ensure that the command `dot', from the
GraphViz package, is in the PATH.  configure should have picked it up.

The "ltl3ba" tab will only be enabled if ltl3ba is available (as
checked by ./configure) and supports options -v/-T/-T3 (checked by the
CGI script).  These option were introduced into ltl3ba version 1.1.0.


Standalone usage
================

Simply run spotcgi.py from this directory.  This will create a directory
called spotimg/ in the current directory (this will hold the generated
pictures) and start an HTTP server on port 8000.  Point your browser
to http://localhost:8000/trans.html and you should be OK.

After you have killed the server process (e.g. with Control-C),
you may want to erase the spotimg/ directory.


Installing on a real web server
===============================

1) Install Spot first (run `make install' from the top-level).

   The CGI script uses the Python bindings and assume they
   have been installed.  Near the top of the script, you
   should see a call to sys.path.insert(), with the expected
   location of the Python bindings for spot.  This path was
   configured from ./configure's arguments and you should not
   have to fiddle with it.  I'm mentionning it just in case.

2) Copy spotcgi.py to some place were CGI execution is allowed.
   Depending on your HTTP server's configuration, you may have
   to rename the script as spotcgi.cgi or something else, so
   that the server accepts to run it.

   Apache users in trouble should look at the following options
   before digging the Apache manual deeper.  These can go
   in a .htaccess file (if allowed).

      # Treat *.py files as CGI scripts
      AddHandler cgi-script .py

      # Allow CGI execution in some directory.
      Options +ExecCGI

3) In the directory where you have installed spotcgi.py,
   create a subdirectory called spotimg/.  This is where
   the script will cache its images and other temporary
   files.  (If you want to change this name, see the imgdir
   variable at the top of the script.)

   This directory must be writable by the Unix user that
   will run the script when the HTTP server processes the
   request.

   spotcgi.py purges old files at most once every hour.

4) Copy the directories css/, js/, and logos/ along with trans.html
   to their destination.  You may have to adjust a few paths at the
   top of the html page.


Debugging
=========

When working on the script, remember that the contents of spotimg/ is
used as a cache and that a request will not be processed again if its
result is in the cache.  So if you don't understand why the change you
have performed has no effect, make sure you are performing some fresh
query, or wipe the contents of the cache (i.e., erase all files inside
spotimg/ but not the spotimg/ directory itself).


The hash string displayed in the web browser is the query string sent
to the CGI script, so you can simulate the call from the command line
with a command like this:

  % export QUERY_STRING="f=a+U+b&r=br&r=lf&r=si&r=eu&o=a&ff=o&mf=d&af=t&ra=t&rf=p&t=fm&fm=od&fm=sm&la=sp&ta=lc&as=ps&ec=Cou99&eo="
  % export SCRIPT_NAME=spotcgi.py
  % export SERVER_SOFTWARE=SimpleHTTP
  % ./spotcgi.py
