A description of the functionality supported by a service, but not the protocols used to access the service. An abstract interface corresponds to a service type. In a Web service, the abstract interface defines the operations the service supports and the formats of the messages that must be exchanged. A WSDL portType defines the abstract interface.
A program that provides an interface to a legacy application. It maps an open API to a proprietary API.
A programming mechanism that allows an application or system function to expose its capabilities to other applications. An API supports application-to-application communication.