An Interface is a service that communicates with clients through a set of standard protocols and technologies.
These Interface standards are implemented in platforms and products from all the major software vendors, making it possible for clients and services to communicate in a consistent way across a wide spectrum of platforms and operating environments.
When you use the term Interface, you are referring to a canonical service model (represented as meta data in the repository) that includes interface descriptions (operations, inputs, and outputs), transport, protocol, and capabilities in terms of IBM® Business Services Dynamic Assembler. In the IBM® Business Services Composition Studio module, you can create meta data models about the Interfaces.
For a Service Oriented Architecture (SOA) to function, the interface model must be standard across the enterprise. The industry standard today is WSDL. In order for heterogeneous distributed component platforms (e.g. Java™ versus .NET) to communicate with one another, the transport and message protocols must be standardized. The industry standard for this today is HTTP and SOAP.
In an enterprise where distributed components are not heterogeneous (e.g. everything is exposed over MQ), you do not need to convert every message to SOAP/HTTP; however every component should still be represented with a canonical service model that includes an interface model, a transport model, and incorporate full IBM Business Services Dynamic Assembler capabilities.
Representing every "service" in the enterprise using this model creates a layer of abstraction which you can leverage to deliver adaptive services using IBM Business Services Dynamic Assembler technology.
The IBM Business Services Composition Studio creates an Interface model based on the port types defined in the WSDL documents. An Interface service model exists for each of those port types, therefore, for a particular WSDL document, you can extract and catalog many WSDL definitions.