Resource Concept and Three-Dimensional State Model

A Resource (or ManagedResource) is any entity, service, or element that can be used by other parts of the system. Most entities in Arda have some aspect of a Resource. Resources share a common, well-defined state model that represents their availability and enables fine-grained management.

The Three State Dimensions

A Resource’s state has three orthogonal parts that together determine whether and how it can be used.

1. Operational State

Indicates the resource’s intrinsic capability based on its internal conditions.

Value	Meaning
`ENABLED`	Resource can perform all its nominal behaviors.
`DEGRADED`	Resource can perform only a subset of its behaviors, or at a reduced standard. Includes reason and capacity details.
`DISABLED`	Resource cannot perform any of its nominal behaviors. Includes reason details.

Transitions:

ENABLED → DEGRADED: partial failure.
ENABLED → DISABLED: full failure.
DEGRADED → DISABLED: further failure.
DISABLED → ENABLED: repair.
DEGRADED → ENABLED: repair.

2. Administrative State

Indicates whether the resource is available for use based on administrative actions, independently of its Operational State.

Value	Meaning
`LOCKED`	Resource is not available for use.
`UNLOCKED`	Resource is available, subject to Operational State and capacity.
`SHUTTING_DOWN`	Resource is currently in use but accepts no new requests.

Transitions:

LOCKED → UNLOCKED: unlock.
UNLOCKED → LOCKED: lock [idle] or force-lock.
UNLOCKED → SHUTTING_DOWN: lock [!idle] (in-use resources cannot be immediately locked).
SHUTTING_DOWN → LOCKED: idle (last usage completes) or force-lock.
SHUTTING_DOWN → UNLOCKED: unlock (lock request cancelled).

3. Usage State

Indicates the current usage of the resource by other system parts.

Value	Meaning
`IDLE`	Resource is not being used.
`IN_USE`	Resource is in use with spare capacity remaining.
`BUSY`	Resource is in use with no spare capacity.

Transitions:

IDLE → IN_USE: acquire [capacity > 0].
IDLE → BUSY: acquire [capacity == 0].
IN_USE → BUSY: acquire [capacity == 0].
IN_USE → IN_USE: acquire [capacity > 0] or release [use > 0].
IN_USE → IDLE: release [use == 0].
BUSY → IDLE: release [use == 0].
BUSY → IN_USE: release [use > 0].

Lifecycle Events

Resources are created via provision and retired via retire. Both events transition all three state sub-machines simultaneously — they are parallel state machines that run from provisioning through retirement.

Application

This three-dimensional model is the standard representation for any managed resource in the system. It supports:

Fine-grained operational control (enable/disable individual components).
Administrative lock-out without affecting operational status.
Capacity management and graceful shutdown.