Domain Modelling

Domain modelling

BlokeBot uses native C# record unions for finite domain states and outcomes with more than two meaningful cases.

Convention

• Keep the union beside its owning domain rather than in a shared catalogue.
• Use a public abstract record with a private constructor.
• Represent cases as nested sealed records with get-only, case-local payloads.
• Provide an abstract typed Match handler for every case.
• Extend Match when adding a case so compiler errors identify every affected consumer.

Avoid

• package or generator dependencies for the union;
• Boolean discriminators;
• enum-plus-null payload bags;
• wildcard/default handlers;
• fallback exceptions for declared cases.

The source note is docs/native-record-unions.md.