In JSF 2.0 (Implicit Navigation is supported), if you have an outcome that does not have a matching view ID in the navigation rules then the outcome will be the view ID itself. This can be very useful to minimize the size of your faces-config.xml.
Suppose we have two pages page1.xhtml and page2.xhtml (under the same directory).
In page1 to go to page2 without declaring any navigation rule in the faces-config, we can say:
<h:commandButton value="Next" action="page2"/>