UML interface: URL iframe integration

I have two applications, A and B, both with a web-based user interface.

Both applications are integrated via an URL iframe mechanism.

A user can click on a link in application A and then gets the UI of application B as am iframe in application A.

Now, since both applications have an interface be开发者_开发问答tween each other (do they?): Who provides the interface and who requires the interface, in the UML sense? What is the main information flow on this interface?

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IMO it depends on the detail level of UML. In a use case diagramm (abstract top level) you would usually show what an actor does with a system.

The "interface" (GUI) used by the actor is composed of your systems A and B, possibly the integrating application C adds some additional functionallity.

In an activity diagramm you could model how data is passed around the systems.

Back to your question: In a component diagram you could show that A,B provide an interface which is used by C (composed).