Process maps are commonly maintained by process analysts who, starting from a top-level overview of business areas and high-level functions, decompose top-level processes into sub-processes. Some or all of the processes in the top-level map are decomposed into sub-processes containing sub-maps and so on down through a number of levels. Architecture areas and business functions are only permitted in the top-level and cannot be created in sub-maps.
It is common practice to decompose processes to four levels in a process map, and then to model the steps of each fourth-level process in a business process diagram (see Linking Processes to Business Process Diagrams).
To create a sub-map inside a process, double-click its symbol. Processes that you create in this sub-map are sub-processes of the initial process and are listed on the Children facet of its property sheet. Their fully-qualified number includes the number of the parent process as a prefix.