LDC-E1347 — Transition carrier of a non-event type

What it means

A transition carries an event: the record in the carrier slot must be built from an event type or a subtype of the event family, with the identifier and timestamp the history is ordered by. A constructor from any other type — a plain record, a memo, anything without that shape — yields a fact no history can read, so the compiler stops at the constructor.

The repair is to carry an event: build the constructor from a declared event with its required fields. A well-carried transition reads under every history.

Example

Arxo Law

language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Tenant;
const Joe: Tenant = entity_ref("urn:law:demo:diagnostics#Joe");
record Memo {
    subject: Text;
}
procedure Review(t: Tenant) {
    state Open initial;
    state Closed terminal;
    transition Decide {
        from Open;
        to Closed;
    }
}
assert attempted_transition(Joe, Decide,
                             Memo { subject: "note" });

Fix

Arxo Law

language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Tenant;
const Joe: Tenant = entity_ref("urn:law:demo:diagnostics#Joe");
event Filed {
    tenant: Tenant;
}
procedure Review(t: Tenant) {
    state Open initial;
    state Closed terminal;
    transition Decide {
        from Open;
        to Closed;
    }
}
assert attempted_transition(Joe, Decide,
                             Filed { id: "ev-1", time: @2026-01-01T00:00:00Z, tenant: Joe });

Engine message

The engine reports this in its own wording:

Output

example.law:19:30: error LDC-E1347: transition carrier: type constructor "Memo" is not a §79 event and not an `Event` subtype — it has neither the `id` the §79.1 value table is collected by, nor `time` whose start orders the §161.1 history

Related

• Procedures — transitions and the carriers they fire on.
• LDC-E1343 — the fields an event constructor must set.