filter sub collection

[Matthew Broadhead]

consider that i have an entity "EntityZ" which has a sub collection list 
of "Detail" entities.  the "Detail" entity has a Date field called 
"archived".

how would i return an "EntityZ" entity with only the "Detail" entities 
where "archived" is null?

i have considered 2 options:
- build a whole new set of objects to populate (seems stupid and wasteful)
- try to not render the objects in front end (in JSF the only way to do 
this seems to be to hide the h:dataTable row using css)