A limitation on aspects of the architecture, its implementation, or its
realization. In contrast to a requirement, a constraint does not prescribe some intended functionality of the system to be realized, but imposes a restriction on the way it operates or may be realized. This may be a restriction on the implementation of the system (e.g., specific technology that is to be used), a restriction on the implementation process (e.g., time or budget constraints), or a restriction on the functioning of the system (e.g., legal constraints). The name of a constraint should be easily understood and is often a short sentence.
