Microsoft proposes a partial typology of Windows Local Accounts in Microsoft, 2019(1) :

The attentive reader will observe the absence of a description for the Non-Default Local System Account. But before getting into that, the first step in analyzing this partial typology is to define its dimensions:

Default vs Non-Default: Per Microsoft, 2019(1), default accounts are built-in accounts created automatically when the OS is installed. Conversely, non-default accounts are non-built-in accounts created after OS installation.

Built-in is an ambiguous term (Built-in (Dictionary Entry)). In effect, the term designates an object that is related to another object for several distinct reasons, e.g. because:

• it forms an integral part of it,

• it is included, made or designed as part of it,

• it was included in it when it was created,

• it is permanently connected to it and cannot be easily removed.

These ambiguities do not allow to classify entities in some grey areas, such as:

• when an account that is an integral part of the OS is deployed by Microsoft after OS installation as part of an upgrade,

• when an account that is an integral part of the OS is deployed as part of the installation of a complementary Windows Component after OS installation,

• when an account that is an integral part of the OS is deployed by a third party (e.g.: an anti-malware system),

• when a custom account is created as part of a custom script during OS installation.

Nevertheless, we may consider that marginal accounts in these grey areas may be classified, especially if the OS editor makes a statement of what it’s classification should be.

In consequence, for operational purposes, we may state that the default vs non-default dimension satisfies in general the properties of exhaustivity and mutual exclusivity. That is to say, a Windows Local Account is either an integral part of the OS or it doesn’t. We should relax the created when the OS is installed condition that is presumably given for illustrative purposes, because Microsoft could deploy a new built-in account as part of an OS upgrade.

It is thus an unidimensional typology (cf. Bailey, 1994, p.3).

System vs Non-System: System accounts are used by the OS and its services.

To privilege concision and readability, definitions are provided via dictionary entries under the References column.