[rights-requirements] descriptive text for sx15

["DeMartini, Thomas" <Thomas.DeMartini@CONTENTGUARD.COM>]

Per my action item, here is some text for a note that can be appended to
sx15:

Note: this requirement differs from R25 in the sense that approval is
not an explicit permission.  (R25 attempts to model a situation such as
a child being given permission to enter an amusement park only if
his/her guardian has given the child permission to leave the house.  In
this (R25) case, the guardian has authority to permit the child to leave
the house and the amusement park owner has the authority to permit the
child to enter the amusement park, but the amusement park owner
conditions his permission on the child having permission to leave the
house.)  SX15, on the other hand, attempts to model a situation such as
a child being given permission to enter an amusement park only if
his/her guardian gives approval.  The guardian does not have the
authorization to give the child permission to enter the amusement park,
as that is something only the amusement park owner can do.

Thanks,
Thomas.