I found some answers to my questions here:
http://www.hibernate.org/159.html
in the "Hibernate Toolset" presentation, where they talk about different Development Scenarios:
(1) Top-down (start with JavaBeans)
(2) Bottom-up (start with relational schema)
(3) Middle-out (start with mapping)
(4) Meet in middle (start with both JavaBeans and relational schema)
They also had a handy diagram here:
http://www.hibernate.org/hib_docs/onlin ... /img6.html
So I guess I could start with UML, generate POJO, generate HBM, and generate DDL. Hopefully I can also annotate a field in my UML with its default value, validation rule, and maybe even some tags specifying the widget(s) to use for viewing, editing and searching that field.
Still not sure what to use for creating a field's widgets (Instantiations SWTDesigner, Jigloo, IBM's Reflexive Interface Builder), and binding them to business objects (Essential Data?), but I guess these are non-Hibernate questions!