I'm looking for some guidelines on writing a technical spec. This spec will be given to contract programmers for writing the business logic in an application. There is no user interaction in these applications, only application to application interaction. So far I've only been able to find information on writing specifications based on user input. I was thinking that maybe UML would be useful for this, but I'm not sure.
If anyone could point me in the right direction I would appreciate it. Thanks!