This use case might apply to console application, or a phone-in call centre. Or a website. You couldn’t tell just by looking at the formal use-case. Indeed, that’s the point — to describe what the system does, without mentioning the technical bits and pieces. (Uncle Bob: “The business rules are agnostic of the delivery mechanism.”)
Data: - Customer email address(required, must be valid) - Customer phone number (required) - HouseId — every house on funda.nl has an Id. Primary Course - The customer issues a “Contact Real Estate Agent” command with above data - System validates all data - System records the fact that the user is interested in the house, so we can notify the agent at a later time. - System confirms to the user that their request has been processed. Exception Course: Validation Error - Processing of the request is cancelled. - System delivers the error to customer.