An actor is the basic structural building block for building systems with ROOM

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```room
// prefixes: abstract and (eventdriven, datadriven, async, sync)
ActorClass ActorName [“An eventdriven ActorClass by default”] {
Interface {
Port port1 …
SPP spp1 …
}
Structure [“Documentation”] {
usercode1 ’’‘ ’’‘
usercode2 ’’‘ ’’‘
usercode3 ’’‘ ’’’
external Port port1
Port internalPort2 …
ActorRef …
Attribute …

         ServiceImplementation of spp1
         Binding ...
         LayerConnection ...
       }
       Behavior ["Documentation"] {
         ctor ''' /* constructor */ '''
         dtor ''' /* destructor */ '''
         Operation ...
         StateMachine ...
       }
    }
    ```
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