ISO/IEC TR 14143-5:2004 describes the characteristics of Functional Domains and the procedures by which characteristics of Functional User Requirements (FUR) can be used to determine Functional Domains. Two example methods for implementing these principles are provided in the annexes.

Either of the methods may be used directly, or by using Functional Domains defined locally by:

• FSM Method to determine if a particular FSM Method is applicable to the Functional Domain(s) represented by their specific FUR;
• Describing, for a given set of FUR, the Functional Domain to which the FUR belong; and
• FSM Method owners and designers describing the Functional Domain(s) to which the FSM Method can be applied as outlined in ISO/IEC 14143-1:1998.