UPDM: Port is an interaction point for a resource through which it can interact with the outside environment.
MODAF/NAF: An interface (logical or physical) provided by a System. A SystemPort may implement a PortType though there is no requirement for SystemPorts to be typed (MODAF::SystemPort, NAF::SystemPort).
DoDAF: An interface (logical or physical) provided by a System (DoDAF::Port).