Templates

Koine ships a set of example domains as templates. The templates/ directory is the single, CI-validated source of truth for every example: the demo project, Koine Studio’s template gallery, and the website’s inline playground all read from it. There is no second copy to drift.

What a template is

A template is a folder containing:

one or more .koi files — the domain model itself; and
a template.json manifest describing it (display name, difficulty, the contexts it defines, and the concepts it teaches).

Single-file starters hold one .koi file; larger domains spread several .koi files across bounded contexts and compile together in directory mode (so imports, the context map, and integration events resolve across files — see Multi-file, imports & modules).

Validation: a green build proves every template

Every template is exercised by TemplatesValidationTests, which on each build:

compiles every template green — so a passing dotnet test proves all templates emit compiling C#; and
validates every template.json against the JSON Schema below — so each one stays well-described, with its id matching the folder name and its entryFile pointing at a real .koi file.

Available templates

Templates carry one of four difficulty levels — starter, beginner, intermediate, advanced — used to order and badge them in listings. (All four are valid schema values; beginner is reserved for future templates and unused today.)

Template	Difficulty	What it models
`starters/billing`	starter	Money, orders, and invariants — the canonical Koine starter
`starters/ordering`	starter	An aggregate with a state machine — renders as a diagram
`starters/contextmap`	starter	Two bounded contexts and the relationship between them
`starters/values`	starter	Smart enums with data, quantities, ranges, and derived fields
`ticketing`	intermediate	A help-desk workflow with a ticket lifecycle and a cross-context SLA policy
`pizzeria`	intermediate	A six-context pizza shop (menu, ordering, kitchen, delivery, payment, promotions) plus an external Gateway
`library`	intermediate	A lending library across five contexts — the Book-vs-BookCopy distinction, loans, reservations, fines
`saas-subscription`	advanced	Multi-tenant subscriptions with trials, metered quotas, dunning, and a payment-provider ACL

The pizzeria template is also the one the demo compiles in place and the one the site’s generated domain reference is built from.

The `template.json` manifest

Each template folder carries a template.json validated against templates/template.schema.json. All fields are required:

Field	Type	Meaning
`id`	string	Stable identifier — must equal the folder name.
`name`	string	Human-readable display name (e.g. `"Billing"`).
`tagline`	string	One-line summary shown in template listings.
`description`	string	A paragraph describing what the template models and demonstrates.
`difficulty`	enum	`starter` · `beginner` · `intermediate` · `advanced` — relative complexity, used to order and badge.
`tags`	string[]	Free-form keywords for search and filtering.
`contexts`	string[]	The names of the bounded contexts the template defines.
`coreAggregate`	string	The headline aggregate that anchors the template.
`entryFile`	string	The primary `.koi` file to open first — must name a file present in the folder.
`teaches`	string[]	The Koine concepts / DDD patterns a learner picks up from this template.
`icon`	string	An icon identifier (an emoji or icon name) for the template card.

Example

{
  "id": "billing",
  "name": "Billing",
  "tagline": "Money, orders, and invariants — the canonical Koine starter.",
  "description": "A single Billing context with Money, an Order aggregate, and the invariants that keep them honest.",
  "difficulty": "starter",
  "tags": ["value-objects", "invariants", "aggregate"],
  "contexts": ["Billing"],
  "coreAggregate": "Order",
  "entryFile": "billing.koi",
  "teaches": ["value objects", "invariants", "aggregates"],
  "icon": "💶"
}