The separation between the automated part of a system and the manual part of a system.

System boundary is the separation between a system and its environment that inputs and outputs must cross whereas Automation boundary is the separation between the automated part of a system and the manual part of a system.

Defining automation boundaries is a technique for generating alternative, high-level, physical system designs. A single set of automation boundaries defines a family of related alternatives, so this technique can be used to identify numerous options. Using automation boundaries to identify alternatives requires expertise in data flow diagrams. Given the trigger events and response time requirements for each process, alternatives are generated by superimposing automation boundaries on the data flow diagram. An automation boundary is simply a line drawn around one or more processes. One possibility is to enclose each process within its own automation boundary. Given even a small data flow diagram, an amazing number of alternative solutions can be generated. If the cost of an alternative significantly exceeds the scope, that alternative is not economically feasible.