This form contains a very interesting feature of ForX. The Interests checkboxes are grouped in a group called interests. This group must have one member checked to be valid by setting forx:grouprequires to any. The last textfield gets a special treatment, as it is only required when the Other checkbox is checked. This behavior is expressed in a conditional requirement expression:
other is the
forx:id of the
Please note, that the textfield does not belong to the group.
This form also contains immediate checked elements, these are validated right after the user entered some data.