Final answer:
Discretionary dependencies must be documented to provide a clear basis for the design's performance and effectiveness, and to articulate the scientific justifications behind decisions within the design process.
Step-by-step explanation:
Discretionary dependencies should be documented because they establish a mathematical and scientific basis for the performance and effectiveness of a design. In a mathematical context, documenting the mathematical model ensures that there is a clear understanding of how the model works and its role in fulfilling the client's requirements. This level of detail is crucial for demonstrating the effectiveness of the design and providing evidence for why certain decisions were taken.
In a scientific context, documenting each step of the design process enables stakeholders to understand the justification for decisions made during development. This includes detailing the science behind chosen solutions, as well as the factors and weights for requirements and constraints that influenced the decision-making process. By thoroughly documenting discretionary dependencies, engineers and designers create a comprehensive record that can be analyzed, peer-reviewed, and improved upon in future projects.