<object>and the new elements like
<progress>) can be anywhere on the page and associated with a form using a form attribute pointing at the id of its form owner.
<input type="text"> ...
<input>is owned by the form foo, as it is contained within it and it does not have a form attribute overriding it.
<textarea>is outside the form, but is still owned by it, as itsform attribute points to the id of its form.