Reference 14 for

14. for

Associates a newly created shape instance with the subject it's about:

Receipt for invoice sentOn: now

for <expr> matches by type, not name: whichever field on the created shape has a type matching <expr>'s type is the one populated — a field typed with a static union matches an expression of any operand's type (## Relationships). When a shape has more than one field of that type, name the field explicitly: Referral for referrer: this.referrer.

Inside a rule body, from { field: value, ... } is the general, clearer way to write this — every field as an ordinary, totality-checked mapping entry, with no field singled out syntactically:

Referral from {
    referrer: this.referrer
    referee: this.referee
    referredOn: now
}

Creating an instance is an ordinary body statement, nothing more — no header annotation is involved. When the created shape serves as a guard witness, the connection to the trigger is the disarm proof's job, checked rather than spelled. for as a query expression ((NurseVerification for this).nurse, exists Shape for expr) is unaffected by this — see ## Predicate expressions, above.