The a4j:region component is used to mark zones which should be processed during Ajax requests without using execute definitions for Ajax behaviors or components. This allows the processing definitions and component identifiers to be decoupled, and declarative wrapping with the a4j:region tag is used instead.

In RichFaces 3.3, the whole view was processed if no regions were specified, as the ViewRoot itself was the region by default. In RichFaces 4.x, all the controls are set to execute="@this" by default according to JSF 2 specifications. However, if the controls wrapped with the a4j:region tag and have no execute definitions, they use execute="@region" instead.

The example below contains two similar user info panels. The button inside the first panel will not work, as it does not use execute declarations; by default it uses execute="@this". A separate definition is needed to make the button work properly. The second panel has its inputs and button wrapped in an a4j:region. This means that the h:commandButton works without any additional execute definitions.

Note: a4j:commandButton/Link use execute="@form"" as their default and so would work as expected in both panels. They also integrate in the core Ajax functionality, and do not require additional a4j:ajax tags.