An implementer may be assigned responsibility for implementing a structural part of the system (such as a class or
implementation subsystem), or a functional part of the system, such as a use-case realization or feature.
It is common for a person to act as both implementer and designer, taking on the responsibilities of both roles.
It is possible for two persons to act as the implementer for a single part of the system, either by dividing
responsibilities between themselves or by performing tasks together, as in a pair-programming approach.