CORBA26 — Interop, 15.7.3 unclear wording

I do have a quick question on one part and that is
Section 15.7.3 IIOP IOR Profile Components. This first paragraph has the
following line in it: " All these components are optional presence in the
IIOP profile
and cannot be dropped from an IIOP 1.1 or 1.2 IOR". Now I must admit that I
am
new to this CORBA thing, but is there something wrong with this sentence?
I am not quite sure what this means and the grammar seems quite odd ("are
optional prensence"?). Any chance someone could translate?

see above