Inclusion of 9th in 11th chords

I was just reading something that said, in addition to the obvious 5th,
that 
the 9th could be omitted (or the implication is that it frequently is)
form 
11th chords.

While we know that the 7th is an im****tant factor, then 9th, to me seems
an 
im****tant player in the 11th sonority.

C-E-G-B-D

C-E-G-D

If we leave off the 7th of a 9th chord, it becomes an "add 9".

C-E-G-B-D-F#

C-E-G-D-F (or F#) obviously)

Is this an add9 add11?

It's similar to:
C D E F G

Which I've seen referred to as add2 add 4.

But it seems like the 9th being present makes the chord very "eleventhy".
As 
a Counter-argument though, if the 9th can't be a "true 9th" until the 7th
is 
present, then the 11th can't use the "fake 9th" to become a true 11th 
itself.

But:

C-E-G-B-F#  seems less "eleventhy" to me.


In addition to the 11th:

7th must be present?
9th must be present?
Both must be present?

Thoughts, ramblings?

Steve