Interceptors are the heart of the command processing system. When a command is executed, the receiver determines the list of interceptors to be run on the command before it's executed. Interceptors are responsible for things such as setting the properties of the command by extracting information from the request and ensuring that the requester has the correct system role.

Each interceptor in the chain has the opportunity to abort the command. For example, the validation interceptor will do this if the parameters required to execute the command haven't been supplied.