Defining required object properties given that a different object property is true.

Hi All,

   Let's consider this simple example (excusing my notation).  Class:Person
requires the following rule when refering to Class:TwinType.    This is not
my actual context, I am simply looking for the proper methodology to define
this restriction/rule..

IF (<individual_Pers1>  hasTwinType  <individual_FaternalTwins) THEN
        THIS MUST BE TRUE  (<individual_Pers1> hasSon Class:Person)  AND (
<individual_Pers1> hasDaughter Class:Person)

  Essentially, I want to specify that if a Person has Twins then that person
must also hasSon AND hasDaughter.  Obviously, this example isn't true in
reality, but I need to define that given that an individual of Class:Person
has an object property to a specific individual THEN  that given individual
of Class:Person must also satisfy two other object property
relationships...

  I am using OWL2 in Protege 4.1.  Any suggestions on how this is defined in
the Equivalent Class definitions?

Thanks!!

-- 
Mitchell Gillespie
MSc. Applied Computer Science
University of Guelph
mgillesp@uoguelph.ca
Cell:  (416) 433-8931