The Cross Community Access profile supports the means to query and retrieve patient relevant medical data held by other communities.  A community is defined as a coupling of facilities/enterprises that have agreed to work together using a common set of policies for the purpose of sharing clinical information via an established mechanism.  Facilities/enterprises may host any type of healthcare application such as EHR, PHR, etc.  A community is identifiable by a globally unique id called the homeCommunityId.   Membership of a facility/enterprise in one community does not preclude it from being a member in another community.  Such communities may be XDS Affinity Domains which define document sharing using the XDS profile or any other communities, no matter what their internal sharing structure.