This excerpt taken from the IILG 8-K filed Jun 17, 2009.
To utilize the exchange privilege, including Special Exchange Services, active membership (paid in full) in good standing must be in effect from the time a deposit is made and/or a request is placed through the actual requested and/or confirmed travel dates and/or the commencement date of the week deposited (whichever occurs later). Further, the Home Resort must be in good standing with II, and the Home Resort accommodations must be available for occupancy as determined by II. A Member Resort will be listed as unavailable for occupancy until such time as II determines that such resort is sufficiently complete to be desirable for exchange. In addition, the Home Resort unit must have check-in/check-out management available on-site at the resort, must be fully equipped and furnished in accordance with II standards, and must have at least weekly maid service.
The exchange service available to II Members is called Dual Exchange because two different methods are available for utilizing the service. Members may choose either the Deposit First or the Request First exchange method.