You have your required procedures, which have to address specific topics, but after that, the definitions and how they interact with one another are up to you so long as you can explain the interaction and use if effectively. A hieratical system is the most common, such as a pyramid.
I've seen 2 places with over 200 employees where the only procedures were the 6 required. Their next level was process materials (high level- mainly flowcharts), followed by instructional materials (very detailed-used for training and reference). These were the labels used by one group, the other I don't recall off the top of my head.