Design Fundamentals: Process Models, Cognitive Principles & Building Great Designers

1. What Is Design?

1.1 Design as Idea, Implementation, and Interaction

Drawing from The Mind of the Maker , design consists of three recursive phases: Idea (an ideal structure conceived in the mind, unconstrained by time or space), Implementation (realizing that idea in a specific medium under constraints), and Interaction (users engaging with the implemented artifact, completing the cycle). The phases operate recursively: implementation creates a space for another design cycle. For example, Mozart implemented his opera idea with pen on paper; the conductor, interacting with that score, conceived an interpretation idea, implemented it with orchestra and singers, and audience interaction completed the process.

1.2 Conceptual Integrity

Great designs have conceptual integrity — unity, economy, and clarity. Frequent discussion of the design concept within a team vastly aids communication; unity of concept is achieved only through much conversation.

2. Design Process Models

2.1 The Rational Model

Described as "an orderly model of an orderly process as the engineer conceives it," the Rational Model proceeds through:

Goal : Start with a primary objective.

Desiderata : Associated desired attributes.

Utility Function : A goodness function weighting desiderata by importance.

Constraints : Every design and optimization is subject to constraints.

Resource Allocations, Budgets, and Crucial Budgets .

Design Trees : The designer makes decisions branching into a tree-structured design space.

2.2 Design as Search Under the Rational Model

Design is conceptually simple: search the tree-structured design space, test each option against constraints for feasibility, and choose to optimize the utility function. Search algorithms are well known.

2.3 Limitations of the Rational Model

Hard to define clear goals and what to design (vague, incompletely specified goals); often overcome by rapid prototyping.

For innovative products, the design tree may be unknown — must explore and discover simultaneously.

Goodness function cannot be evaluated incrementally.

Experience and simple estimators are insufficient.

Desiderata and their weightings keep changing.

Constraints keep changing, including constraints outside the design space.

Despite criticism, the waterfall model based on the Rational Model remains widely used in industry.

There are two distinct interpretations of engineering design. The problem-solving approach, popular in many tertiary institutions and with an emphasis on solving structured, well defined problems using standardized techniques, may be traced to "hard" systems thinking. The creative design approach, on the other hand, combines analytical and systems thinking with human factors in engineering design to create and take advantage of opportunities to serve society. This paper discusses the limitations of the problem-solving approach in dealing with many real world tasks.

2.4 Alternative Models

Models simplify reality; each emphasizes different aspects. Better models should emphasize progressive discovery and evolution of design requirements, be memorably visualized for teaching and stakeholder understanding, and still facilitate contracting among fallible humans.

Co-Evolution Model

It is widely accepted that creative design is not a matter of first fixing the problem and then searching for a satisfactory solution concept; instead it seems more to be a matter of developing and refining together both the formulation of the problem and ideas for its solution, with constant iteration of analysis, synthesis and evaluation processes between the two "spaces" — problem and solution.

This model emphasizes incremental discovery and evolution, formal requirements specification, and visualization. Its shortcoming: lacks clear milestones and contracting points.

Raymond's Bazaar Model (from The Cathedral and the Bazaar )

Open-source communities like the Linux kernel use the bazaar model. Key characteristics:

Modularity (pipes and filters).

Gift-prestige culture — reputation from community, not just monetary reward.

An overall system architecture must exist (e.g., UNIX).

Builders are also users.

Boehm's Spiral Model

Emphasizes prototyping.

Starts with user-interface prototypes.

User testing long before an operational prototype is possible.

However, it does not emphasize contracting points. The author values the Spiral Model most and believes it deserves continued development.

3. Collaboration in Design

As technology matures and competition intensifies, design shifts from individual to team design. The core challenge: maintaining conceptual integrity across the team.

System Architect : Empower a single chief architect for final decisions. "The most important single way to ensure conceptual integrity in a team design is to empower a single system architect."

One User-Interface Designer .

Valuable collaborative activities:

Determining Needs and Desiderata from Stakeholders — identifying implicit objectives and constraints.

Conceptual Exploration — Radical Alternatives — brainstorming, competition as an alternative to collaboration.

Design Review — demand multidisciplinary group review, use graphical representations.

4. Design Cognition

4.1 Rationalism vs. Empiricism in Design

Rationalism : Humans are rational; software design is like mathematics and can be designed correctly by pure thought. "Design software to be correct and then prove the design is correct. A program is a pure mathematical object and in principle can be designed perfectly by correct thought."

Empiricism : Humans inevitably make mistakes — in defining objectives, architecture, implementation, and code. Practices: early prototypes, early user testing, iterative incremental implementation, testing on a rich bank of test cases, regression testing after changes.

The author sides with empiricism: "Can I, by sufficient thought alone, design a complex object correctly? No; testing and iteration are in practice necessary. But careful thought helps."

4.2 User Models — Better Wrong than Vague

An explicit, articulated guess about users beats an unspoken assumption. Wise designers write down what they don't know but assume about users.

4.3 The Budgeted Resource

Identify the scarce resource (often not dollars). Name it explicitly, track it publicly, control it firmly.

4.4 Constraints Are Friends

Constraints shrink the designer's search space. Distinguish four types:

Real constraints .

Obsolete once-real constraints (e.g., outdated technical limits).

Constraints misperceived as real — tell what properties you need, not how they are to be achieved.

Intentional artificial constraints .

4.5 What Is Elegant Design?

Technical aesthetics ( Esthetics ) rests on three pillars:

Parsimony : "Elegance requires parsimony" (Einstein: "Everything should be made as simple as possible, but not simpler").

Structural Clarity : The basic structural concept must be plainly evident and easily explained. Familiar metaphors aid both elegance and comprehensibility, especially in user interfaces.

Consistency : Given partial knowledge of the system, one can predict the remainder. From consistency flow three principles:

Orthogonality : Do not link what is independent.

Propriety : Do not introduce what is immaterial (e.g., signed zero).

Generality : Do not restrict what is inherent (a thing applicable in multiple places).

Style : "Style is the dress of thought, and a well-dressed thought, like a well-dressed man, appears to great advantage." Hypothesis: minimization of mental effort. Consistency across micro-decisions. To get a consistent style — document it (e.g., coding standards). "A design team must document the design proper, whether in engineering drawings, building blueprints, or a user manual."

4.7 Exemplars in Design

Exemplars provide safe models for new designs, implicit checklists of design tasks, warnings of potential mistakes, and launching pads for radical new designs.

The designer should know well the exemplars of his craft, their strengths and weaknesses. Originality is no excuse for ignorance.

Designers who master predecessors' styles have more treasures for their originality to draw upon.

Mastery requires not laziness but high enthusiasm and diligence.

4.8 How Expert Designers Go Wrong

Study failure examples even more carefully than successes.

Watch yourself after success.

Think at the top level about the object and its environmental assumptions. Is a paradigm shift under way? Will assumptions hold a decade hence? Are you designing the right thing?

4.9 Documenting Design Trajectory and Decisions

For designers to get the most learning from each design experience, they need to document how it evolves: not only the whats of the design, but also the whys by which it was reached.

Capture the implicit design tree (how to capture) — currently no good tools exist.

5. Great Designers — How to Cultivate Them

5.1 Great Designs Come from Great Designers

By its very nature, a product process is veto-oriented, aimed at blocking bad ideas and catching oversights.

Design process can raise the low end of the design curve and improve average performance.

A wise leader organizes by drawing responsibility boxes around the people he has, not by putting people into abstractly ideal boxes.

Great designers require bold leaders who demand innovation.

Go for conceptual integrity: entrust your design to a chief designer.

5.2 Where Do Great Designers Come From?

Great designs come from great designers, not from great design processes.

Critiqued practice.

Make the dual ladder (technical and management tracks) real and honorable.

Plan formal educational experiences.

Plan a varied set of work experiences — "the course of the young career should itself be designed — for variety, for depth of involvement, for spiraling challenge and responsibility."

Protecting Great Designers at Work

Protect them from distraction (flow should not be interrupted).

Protect them from managers.

Protect them from managing (avoid promoting good designers into management roles).

How to Become a Great Designer

Constantly sketch designs — learn to design by designing.

Seek knowledgeable criticism of your designs (Donald Schön, Educating the Reflective Practitioner ).

Study exemplars and precedents — "What led such a smart designer to do that?" A self-education project.

Journal : Keep a dated journal of design questions, decisions, and reasons, covering:

Assumptions, hypotheses, constraints.

Budgeted cost and whether you can manage it.

Expected metrics (explicit and implicit).

Decision criteria when multiple candidates exist.

Use of graphical tools.

6. 记录你的设计design trajectory（轨迹）

Assessment: good points and weaknesses.

6. Summary

This book explores many essential questions of design; it serves as a reference when confusion arises.