Which quality is vital for the requirements to be considered successful across all parties involved in a project?

The quality of consistency is vital for requirements to be deemed successful across all parties involved in a project because it ensures that all stakeholders have a shared understanding of what the requirements entail. Consistency means that the requirements do not conflict with one another and that they are stable throughout the project lifecycle. When requirements are consistent, they facilitate clear communication among team members, reduce the likelihood of errors, and align the objectives of different stakeholders.

In a collaborative environment, inconsistencies can lead to confusion, misalignment, and ultimately project failure. When everyone involved understands and agrees on consistent requirements, it enhances collaboration and fosters a cohesive project vision. This consistency builds trust among the stakeholders, ensuring that their needs and expectations are managed effectively and are coherent throughout the project's execution.

The other qualities listed—changeability, traceability, and prioritization—while important in their own right, do not carry the same overarching importance across all parties in terms of shared understanding and agreement as consistency does.