Domain

A domain is the top-most definitional level in RIDDL. We use the word domain in the sense of a knowledge domain; like an entire business, a field of study, or some portion of these. It has nothing to do with Internet domain names. A domain is an arbitrary boundary around some subset of concepts in the universe. As with Domain Driven Design, RIDDL uses the concept of a domain to group together a set of related concepts.

Domains in RIDDL are inert. That is they only serve to contain definitions that do things, but they don't do things themselves.

Domains can recursively contain other nested domains so that a hierarchy of domains and subdomains is established. Because of this, we can organize any large, complex knowledge domain or field of study, into an hierarchical ontology.

For example, if you were modelling the domain of Two Wheeled Vehicles you might devise a domain hierarchy like this: * Two Wheeled Vehicle - Motorized - ICE powered motorcycles - Scooter - Electric Bicycles - Segway * UnMotorized * Bicycles * Oxcart * Handtruck * Human With Training Wheels

Cross-Context Definitions

Domains are inert, but two definitions may live at domain scope precisely because they span the contexts beneath it:

• A Repository that synthesizes data from entities in several contexts, and is queried by several contexts
• A Connector whose two ends are ports in different contexts

Both are validated for correct scope. A domain-scoped repository that reaches only one context is an Error — it is provably unnecessary there. A context-scoped connector whose ends cross contexts is likewise an Error, and so is the reverse.

Authorship and Attribution

A domain is one of only two places an author may be defined (the other is a Module); everywhere else, authors are referenced with by author Name. A domain may also declare a version and a copyright.

Validation

A domain that identifies no author — considering its own author references and defined authors, as well as those of any enclosing domain — draws a MissingWarning. It is suppressible through the existing missing-warning gates.

Occurs In

• Root
• Modules
• Domains — domains can be nested in a super-domain

Contains

flowchart TD
    Domain(["Domain"]) --> Context
    Domain --> Epic
    Domain --> Saga
    Domain -->|nested| Domain
    Domain -.->|spans contexts| Repository
    Domain -.->|spans contexts| Connector
    Domain --> Defs["Type · User · Author<br/>Version · Copyright<br/>Comment · Include · Import"]

• Context — the bounded contexts of the domain
• Domain — nested subdomains
• Epic and Saga
• Repository and Connector — only when they genuinely span several contexts
• Type, User, Author, Version, Copyright, Comment
• Include and import directives