CERN JUG Meet-up #5 - Lessons from Spec-Driven Development

Tuesday 12 May 2026, 18:00 → 20:00 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

Welcome to the CERN Java User Group Meet-up #5 - Lessons from Spec-Driven Development

This event offers a unique opportunity to those passionate about Java and modern engineering practices to engage with the CERN developer community and beyond. Whether you are a CERN member or an external visitor, we invite you to join us for an evening of learning and networking.

• Registration: To subscribe to news about future events and meetups, please use the CERN JUG mailing list. Those of you coming from the outside of CERN will need to create a guest account as explained here.

• External visitors: If you are coming from outside CERN, we will arrange a badge for you upon registration. Badges are necessary for site access and will be printed for your convenience.

• Date & Time: 12 May 2026, 18:00–19:30

• Venue:  4/3-006 - TH auditorium, CERN

 

For any questions, please contact the organizing team at cern-jug-organizers@cern.ch.

 

 

18:00 → 18:50 Lessons from Spec-Driven Development

In many projects, specifications and code drift apart over time. Requirements change, documentation becomes outdated, and developers rely mainly on the code. This increases risk and makes changes harder, especially in long-lived business applications.

This talk presents a spec-driven approach where system use cases are the central artifact. A system use case describes observable system behavior and acts as a stable contract for the application. Code is derived from these use cases instead of treating the code itself as the source of truth.

AI is used as a supporting tool to generate and update code and tests from system use cases in small, controlled steps. The focus is not on full regeneration, but on keeping existing code and specifications aligned over time.
Using concrete examples, the talk shows how backend logic, database access, and UI behavior can evolve together. It also explains when code is generated, when it is updated, and how version control and reviews help keep changes small and understandable.

The session shares concrete workflows and lessons learned from daily Java development, including limitations and trade-offs of using AI in this way.

Speaker: Mr Simon Martinelli

18:50 → 19:30 Networking drinks