[xwiki-devs] inheritance or new datatype ?

Hi devs, It is possible to define two XWiki classes with a relationship of inheritance? Example: I have MyDocumentClass and MyHeaderClass, it is possible to say all properties of MyHeaderClass are properties of MyDocumentClass ? Maybe I should prefer composition to inheritance ;-) So, can I define a new datatype (like Number, String, TextArea, …), and create a propertie of type MyHeaderClass in the definition of MyDocumentClass ? Thanks, Benoît