A port typed by required interface is both a connectable element and a structural feature of an encapsulated classifier. The required interface specifies the services that the classifier uses (requires) through the port. Requests that arrive at the port are provided by the classifier that realizes the interface specified by the port.
Explanation
A port that is typed by a required interface expresses what is required at the port. The interface contains abstract operations that specify the contract that the classifier has with its environment. The port separates the internal working of the classifier from its environment and the interface stands as a formal contract on the type of information that is required at the port.
