A special situation exists when a system and its software are both being defined concurrently. Then the functionality,
interfaces, performance, and other attributes and constraints of the software are not predefined, but
rather are jointly defined and subject to negotiation and change. This makes it more dificult, but no less
important, to meet the characteristics stated in 4.3. In particular, an SRS that does not comply with the
requirements of its parent system specification is incorrect.