Resource

The Resource semantic module describes what an application provides and what its work consumes:

• A resource is an entity that can be claimed, such as a thread, worker, or memory pool.
• A capacity is a named quantity provided by a resource.
  • An occupancy is a quantity held throughout a usage. For example, a task might occupy 256 bytes of a memory pool until it leaves its current state.
  • A rate records a total quantity processed during a usage. For example, a transfer might process 1,024 bytes. Dividing that value by the usage duration gives the observed transfer rate.
  • A resource with no named capacities is a unit resource. Each usage claims the entire resource instance.
• A usage is a claim on a specific resource instance. It identifies the resource and records how much of each capacity is claimed.
• A bound is a reported upper limit for a capacity. Bounds belong to the resource and may be updated by its events.

A resource can be declared on an entity under either entities or fsms. An FSM can therefore provide a resource while also modeling its own lifecycle.

Only entities modeled as FSMs can use resources.

Why can only FSMs use resources?

Entering a state starts the usages declared by that state, and leaving it ends them. A final state cannot start a usage. The validated FSM topology therefore gives every usage a modeled way to end.

This is a schema-level guarantee, not a runtime guarantee. The instrumenting code remains responsible for emitting a valid transition out of a state that uses resources. If it does not, the event stream contains a logically unended usage.