Sub forms

This is either a question naivetee or a feature request: a way to add subforms to a piece of content.
Instead of a text field or an option field: a field that hold a reference to another form. This way you could have one or two or 100 pieces of content. That references another form in its own right. All of the CCK created forms can be added to any form.
In admin, this would be one reference to content. There would be a cross reference table of what subforms connect-- parent to child tables.
In the front end, there would be a cross reference table of subform content pieces to the subform element.
Example:
Content piece 25 has a subform of three elements.

 ---------------------------------------------------
| parent_table | parent_ref | child_table | child_ref |
 --------------------------------------------------
| review       | 25         | ref_text    | 15        |
| review       | 25         | ref_text    | 19        |
| review       | 25         | ref_text    | 44        |
 --------------------------------------------------

When the content is loaded and it encounters a subform reference, it will look to a cross-reference table and load all of the form material recursively.