|  | 
The Asio asynchronous model is enabled by the library elements listed in the table below.
| Library Element | Description | 
|---|---|
| 
                     | Defines valid completion signature forms. | 
| 
                     | Determines whether a completion handler is callable with a given set of completion signatures. | 
| async_result trait | Converts a completion signature and completion token into a concrete completion handler, and launches the operation. | 
| async_initiate function | 
                    Helper function to simplify use of the  | 
| 
                     | Determines whether a completion token produces a completion handler for a given set of completion signatures. | 
| associator trait | Automatically propagates all associators through layers of abstraction. | 
| 
                    associated_executor
                    trait,  | Defines an asynchronous agent’s associated executor. | 
| 
                    associated_allocator
                    trait,  | Defines an asynchronous agent’s associated allocator. | 
| 
                    associated_cancellation_slot
                    trait,  | Defines an asynchronous agent’s associated cancellation slot. |