A specialized Condition model where a Server can interact with a User. The information flow starts with the Server sending a message (a dialog prompt) and a number of possible responses. The User selects one of these responses which the Client then sends to the Server.
Dialogs are typically used in states that require intervention by a Client. For example, a Server monitoring a paper machine indicates that a roll of paper has been wound and is ready for inspection. The Server would activate a Dialog Condition indicating to the user that an inspection is required. Once the inspection has taken place the user responds by informing the Server of an accepted or unaccepted inspection allowing the process to continue.