Entities and fields

A field is name: type followed by any modifiers:

app billing "Billing" {}

entity Invoice "Invoice" plural "Invoices" {
  number:    text required
  customer:  ref Account on delete restrict
  issued_on: date
  total:     money USD
  terms:     longtext help "Shown on the printed invoice."
  ssn:       text pii hidden
  status:    enum draft, sent, paid
  net:       computed number = total - discount
  notes:     json
  age_days:  number validate age_days >= 0 "Age cannot be negative."
}

The types are text, longtext, number, money <currency>, boolean, date, datetime, file, json, enum, ref and computed. The modifiers are required, pii, hidden, label, help and validate <expr> "<message>".

Two things worth calling out. pii is not decoration — it marks the field as personal data for the platform's handling of it. And a ref must say what happens when its target is deleted (restrict, nullify or cascade); there is no silent default, because the wrong answer is discovered in production.

Two entity shapes exist beyond the ordinary one — an append-only ledger, and a rollup that is derived rather than written:

app ledgers "Ledgers" {}

entity AuditEntry ledger {
  actor:  text
  reason: text
}

entity AccountTotal rollup over Invoice sum total by customer where status == "paid"