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Research · White Paper Series

What keeps software changeable?

The Changeability Trilogy

Three white papers and a synthesis on how engineering teams keep software quick to change as it grows. Published for majcon’s 20th anniversary, May 2026.

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The Trilogy

Each paper answers one question. Together they form a single system: the developer (ACE), the structure (CDD), and the economics (EoC), connected by the synthesis.

1 · Who develops well?

The ACE Model

Technical training alone does not transform teams. The ACE Model describes three developmental dimensions (Analytical, Creative, Emotional) that together define the complete software engineer.

By Damir Majer · Prof. Dr. Christian Drumm · 12 pages · May 2026

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2 · How do you enforce quality?

Constraint-Driven Development

Tests catch individual failures. Structural constraints prevent whole classes of them. The Constraint Stack links six levels to the defects each one rules out.

By Damir Majer · 13 pages · May 2026

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3 · What do you optimize for?

The Economics of Changeability

As a system ages, the cost of each new feature rises. This paper argues that changeability is the economically central quality attribute, and introduces the Feature Cost Index as an early-warning signal.

By Damir Majer · 13 pages · May 2026

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More in the series

Synthesis: how it all connects

The Five Rings

The synthesis of the trilogy: developer, structure, and economics form a single system. AI amplifies existing discipline rather than replacing it.

By Damir Majer · 8 pages · May 2026

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The practical companion

AI Technical Health Playbook

A standalone practitioner playbook: how teams measure and protect technical health in the age of AI.

By Damir Majer · 22 pages

AI Technical Health Playbook

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From theory to practice

These papers describe what matters. The next step is a conversation about your team and your codebase.

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