Domain Driven Design

I’m prone to being overly enthusiastic when something seems to fit perfectly puzzles I try to solve. Right now I’m in that state exactly. Ubiquitous language is the answer to so many pains of agentic coding. Part of my current experiment vocabulary started as “Workflow”, then it gave birth to sibling “Component”, then “Fabric” was extracted from “Component” when its meaning got refined, and then “Fabric” revealed “Substrate” underneath. Each of the evolving terms guiding both me and the agents in the correct direction, constraining what conceptually makes sense within the bigger picture defined by vocabulary. ...

Adopting ubiquitous language (where agents are heavily responsible for keeping you, the codebase, and the vocabulary in alignment—otherwise, drift will kill you) greatly improves alignment between what you want and what agents deliver. There is still tactical cognitive debt. You have no idea about the details of delegated implementation, but that’s OK. You decided to be a Lieutenant General, not a Lieutenant, so you move divisions, not platoons. You note that a particular operation introduces side effects that break everything that follows. You can change the implementation to mitigate them; you can ask an agent to do it—it might be enough to move forward. Until a minute, hour, day, or month later, when you or an agent breaks the silent, tribal contract you made by fixing the implementation to be pure and idempotent. It won’t fly at scale. Shit, it won’t fly even in domain discovery mode for a non-trivial personal project. ...

Separating domain entities from ORM models is often dismissed by developers and managers as ‘over-engineering’. Yet, long ago I lost count of how many times a promised ‘simple CRUD’ app turned out to be neither simple nor CRUD. It was just hard to reason about, because the ORM models had outstayed their welcome as a proper domain substitute. 1. The Write vs. Read Symmetry Fallacy The ORM creates a false impression that writing and reading data to and from persistence are the same responsibility. Yet, we care about correctness when writing and performance when reading. There is no symmetry here. ...