The following terms are used in the context of open money software (see specification):
A string of characters uniquely identifying an entity (a user identity, a currency, an account or a namespace).
An entity enclosing/containing names of entities, including other namespaces.
A namespace enclosing another namespace is referred to as the parent of the latter, and the latter is referred to as a child of the former. The nesting of namespaces leads naturally to the extension of these terms in both directions: grandparents, great-grandparents, etc. (ancestors collectively) and grandchildren, great-grandchildren, etc. (descendants collectively).
Every name is unique within the namespace containing it but the same name may appear in any number of other namespaces.
In general there is no relationship between entities identified by the same name enclosed within different namespaces. The one exception is that a secondary identity enclosed within one namespace may optionally have the same name as the associated primary identity enclosed within a different namespace.
A user is an entity holding/owning one or more accounts.
A user may be a person, an organization or a machine/device.
Every user has a unique primary identity defined within a namespace, and that namespace is referred to as a registry in that context.
Every user may have one or more secondary identities, each contained within a different namespace with the authorization of that namespace's steward(s).
A user's primary identity provides access to the open money instance by defining a unique identity associated with a real world entity along with everything used to authenticate that association.
A user's secondary identity relies upon the assocated primary identity to provide access to the open money instance.
However, the accounts held/owned by any secondary identity are distinct from those held/owned by the associated primary identity and from those held/owned by any other secondary identity associated with it.
An account is a variable associated with (and its characteristics defined by) a currency with the authorization of that currency's steward(s).
An account is owned/held by either a primary identity or a secondary identity.
A steward is a user holding a position of authority or ownership over a named entity.
A currency is a variable type with which at least two accounts are associated. Within the context of open money, these accounts always sum to zero. (Within the extended context of open measures, that restriction does not apply. However, that is beyond the scope of this section.)
An instance of open money is a distinct tree of namespaces.
A (web) server may host any number of distinct instances.
A longer term (and low priority) objective is to enable any such tree to be grafted on to (i.e. moved to within) any namespace within a distinct instances, thereby forming a new instance. The root of an instance cannot be grafted on to a namespace within itself; otherwise this would create a loop.
A registry is any namespace in which primary identities are defined.
Upon logging into any open money instance using its primary identity, that registry is the namespace in which that user starts.
Upon logging into any open money instance using any secondary identity, the user lands in the namespace enclosing that secondary identity.
In either case, the complete user.namespace string is necessary to identify the user identity when logging in.
The following terms are used in the wider context of open money and open measures:
Open money is a special case of open measures in which all accounts are scalar variables and where all accounts in a specific currency sum to zero.
Examples of open money units include physical quantities (such as time, length or energy1) and counts.
A special but important case of open money, from which its name derives, is a unit metrically equivalent2 to, but distinct from, the unit of legal tender in use locally. Such a currency is money and has significance only in the context provided by that legal tender, and both are money.
The only operation associated with open money is payment.
The term money refers to anything accepted as settlement of an obligation or commitment. A payment accepted in open money is de facto money.
In the context of open money, a payment is the simultaneous adjustment by the same amount of two accounts in the same currency, one (the payer) being decreased and the other (the payee) being increased.
Open measures generalizes open money to include compound currency types and their many associated operations, and places no requirement for the accounts in a specific currency sum to zero.
See open measures.
The term energy refers strictly to a quantity with physical dimensions ML2T-2. A typical use would be for accounting in energy generation, storage, use and loss in electrical microgrids at various scales.
The term metrically equivalent in this context means that goods and services are priced the same for legal tender (a national money) and its local open money counterpart, whichever is accepted as payment and in whatever proportion.