I'm looking into doing the following: I have a program written in Common Lisp, which I want to be able to communicate with Emacs. The program deals with natural language parsing, so the things I'd need to access in Emacs would be the contents of the buffer and some minimal preliminary parsing required to create messages to send to the Common Lisp program. The Common Lisp program will then process the messages and reply to the Emacs Lisp program, so that it will display the results.
I understand that SLIME would be a good tool to use to achieve this, mainly because it already does most of it, but looking into documentation I find that it's a "user documentation" kind, not a "developer documentation". Essentially, I would like to know what is the minimum that I could use on the Emacs Lisp side to get the communication going (I certainly don't need the introspection, or REPL in this case, all I need is to send messages to and from my program running in SWANK).