It is possible to pass a callable-method reference (of a process) to an ivy component dialog. The component can then call this process method (from a the parent dialog) at any time.
There is a demonstration of this feature in the HtmlDialogDemos project, which is bundled with the Designer in the *applications/samples* folder. Check out the implementation of the *ch.ivyteam.htmldialog.demo.component.MethodCallbackDialog* and its child *ch.ivyteam.htmldialog.demo.component.DetailListComponent*
So to be clear you can not call logic of another process within a component process directly. But the component view can interact which logic from a parent process. Maybe you could simulate the call from the composite process to the parent process by using the [Request Context][1] to fire a hidden view effent that will trigger the parent process.
[1]: http://www.primefaces.org/showcase/ui/misc/requestContext.xhtml
