Account

A singleton account — a single, named, 1-of-1 thing the institution holds. Every Account has an id (the stable database identifier), a role (the abstract slot the rest of the L2 model refers to — e.g. CashDueFRB, DDAControl), and a scope of either internal (the institution's own ledger account) or external (a counterparty: the Federal Reserve, a card processor, a beneficiary bank).

Accounts can roll up via parent_role: a sub-ledger holding account typically points to a control account that aggregates many sub-ledgers. The drift, overdraft, and limit-breach matviews use the parent relationship to compute parent-level rollups in addition to the leaf view.

The two scopes drive different downstream behavior:

• internal accounts participate in double-entry — every Rail that posts to one expects an offsetting credit/debit. They show up in the L1 invariant matviews (drift, overdraft) and in the per-day Daily Statement.
• external accounts stand for counterparties; the institution does not own them. They appear as the other side of inbound / outbound flows, and the Investigation app's account-network sheet walks edges through them.

An Account is a physical, 1-of-1 thing. For a 1-of-many shape (per-customer DDA, per-merchant settlement) you want an Account template instead.

Specific example for you