Cheat sheet
DDD words
The words of this course, one meaning each. New words join after each lesson.
From Lesson 1
| Word | Meaning | probat8 example |
|---|---|---|
| Domain | The part of the real world the software is for. | Bat protection at wind turbines. |
| Domain expert | A person who knows the domain best. Often not a developer. | Bat biologists, consultants, authorities. |
| Ubiquitous Language | One shared set of words, used by the whole team in talk, docs, screens and code. | One word for the shutdown values, used everywhere. |
| Bounded Context | A part of the system where each word has exactly one meaning. (More in a later lesson.) | “operator” can mean one thing here, another thing there. |
Sources: Eric Evans, DDD Reference (Definitions, p. vi); Martin Fowler, Ubiquitous Language.
Two word problems to spot
| Problem | Looks like | Cost |
|---|---|---|
| One word, many meanings | “operator” = company, uploader, admin staff, comparison sign | Questions, wrong guesses |
| One thing, many words | Shutdown values: four names in docs, backend, frontend, screen | Translation in your head, bugs |
Fix a word in four steps
- Collect every meaning, and where you found it.
- Ask a domain expert what they mean.
- Pick one meaning per word. New words for the other meanings.
- Use it everywhere: talk, docs, screen, code.
Two real meanings, both needed, in different parts of the system? That hints at two Bounded Contexts.