I've added example # 3 to illustrate how to use an <af:selectBooleanCheckbox> bound to VARCHAR2 or NUMBER Oracle Database columns.
This is performed by creating a transient attribute of type Boolean and redefining its getter and setter methods to 'translate' the ADF Business Components type Boolean to the 'standard' String or Number types that the Oracle Database "understands".
(Boolean is not a valid type in the Oracle Database).