Question About making two cloudstack talk to each other

[Amira Okasha]

Dear sir,
I am a Master degree student and it is requested from me to do a communication 
between two open source cloud stack
using OCCI and because i am new to installing clouds i can't understand the 
meaning of making two clouds talk to each other and how .
inter cloud is also making two clouds communicate with each other so please 
advice how it is done or refer to a manual or something.
B.rgds
Amira Okasha