Bounded Context

A Bounded Context is the largest unit inside which a single, consistent vocabulary applies. The same word can mean different things in different Bounded Contexts; inside a Bounded Context, every term has exactly one meaning.

Bounded Contexts live inside the Domain (and may be classified by a Subdomain). They hold the consistency units that actually do the work – Aggregates, Dynamic Consistency Boundaries, Process Managers, and Read Models.

Why the Boundary Matters

The boundary is a translation point. When a concept crosses from one Bounded Context to another, you don't carry the meaning along; you re-interpret. A customer in a sales Bounded Context might be a Lead, and the same customer in a billing Bounded Context might be an AccountHolder. Both are real, both are right, and the Bounded Context is what tells you which one you're in.

That is why a Bounded Context is also the place where Context Mappings become meaningful. A Context Mapping describes how two Bounded Contexts translate between each other – which parts of one are exposed, which parts of the other are consumed, and what shape they take in the middle.

The Ubiquitous Language

A Bounded Context's most valuable artifact is its ubiquitous language – the canonical terms that apply inside it, each with its definition. The language is one entry per term, deliberately without aliases: the whole point of choosing one term is that there is one term. Where helpful, an entry can also list rejected alternatives, so a reader who looks up a synonym still lands on the canonical word.