Design Rationale

Design rationale explains the reasoning behind design system decisions. Articulating design rationale helps stakeholders understand choices, enables principled future decisions, and prevents revisiting settled questions without new information.

What Is Design Rationale

Design rationale is the explanation of why design decisions were made. It goes beyond documenting what was chosen to explain the reasoning, constraints, and tradeoffs that led to the decision. Rationale captures the thinking process, not just the outcome.

Rationale serves educational and practical purposes. It helps people understand the system deeply rather than superficially. It guides future decisions facing similar tradeoffs. It enables informed discussion when revisiting decisions becomes appropriate.

How Design Rationale Works

Context description establishes the situation that required a decision. What problem needed solving? What constraints existed? What stakeholders were involved? Context helps readers understand the decision environment.

Options enumeration describes alternatives that were considered. What approaches could have been taken? What were the tradeoffs of each? Showing that alternatives were considered demonstrates thoroughness.

Selection explanation articulates why the chosen option was preferred. What criteria determined the choice? How did the selected option compare against alternatives on those criteria? Selection rationale is the core of design rationale.

Consequence acknowledgment addresses expected outcomes. What benefits does the decision provide? What limitations does it create? What ongoing considerations result? Acknowledging consequences demonstrates honest assessment.

Key Considerations

• Rationale should be captured while context is fresh
• Honesty about tradeoffs builds credibility
• Rationale documents should be accessible to stakeholders
• Rationale enables informed revisiting when circumstances change
• Excessive detail can obscure key reasoning

Common Questions

When should rationale be documented?

Document rationale for significant decisions that establish patterns, resolve notable tradeoffs, or address recurring questions. Not every small decision needs formal rationale. Focus on choices that shape system direction or that future team members will want to understand.

How detailed should rationale be?

Detail level should match decision significance and audience needs. Major foundational decisions warrant thorough treatment. Smaller decisions may need brief explanation. The goal is communicating key reasoning, not exhaustive documentation.

How does rationale help with future decisions?

Rationale helps future decisions by revealing the reasoning that can be applied to similar situations. Understanding why past decisions were made enables consistent application of similar logic. Rationale also indicates when circumstances have changed enough to warrant different choices.

Summary

Design rationale explains the reasoning behind design system decisions through context, options, selection explanation, and consequence acknowledgment. Success requires capturing rationale while context remains fresh and presenting it accessibly. Organizations should document design rationale to enable understanding and guide consistent future decision-making.