The Expose Interface element is a graphical method of depicting the required or supplied interfaces of a Component, Class or Part, in a Component or Composite Structure diagram. It just identifies the fact that the element provides or requires an interface; to depict the fact that the provided interface is used, or the required interface provided, by another element using the Assembly connector.
The Expose Interface element must be attached to the Class or Component element, and it becomes a child element of that Class or Component; it cannot exist independently. You can attach more than one Expose Element to another element.
When you create the Expose Interface element, a dialog displays in which you enter a name for the element and specify whether it represents a required interface or a provided interface.