18. An apparatus configured to make policy decisions applicable to a user within an IP Multimedia Subsystem, the apparatus comprising: a processor configured to: identify a group of which the user is a member; generate a request for policies and dynamic data stored in a Group Document of the identified group; a transmitter configured to send the request to a Group XML Document Management Server (XDMS); a receiver configured to receive a response from the Group XDMS, the response including the policies and dynamic data stored in the Group Document of the identified group, wherein the policies of the response includes policies that are applicable to the group as determined by combining policies of related groups identified within the Group Document with a users' group of the Group Document, wherein the combining policies with the policies of the identified related groups comprises any of: if a policy of the user's group contradicts a corresponding policy of a superior one of the identified related groups, overriding the policy of the user's group with the policy of the superior related group; and if a policy included in the user's group is narrower than a corresponding policy of a one of the identified related groups, overriding the policy of the superior related group with the policy of the user's group; wherein the policies comprise a maximum number of session in which members of the group are allowed to participate simultaneously; wherein the dynamic data comprises the number of sessions in which members of the group are participating; the processor is further configured to evaluate the policies using the dynamic data in order to make policy decisions.
18. An apparatus configured to make policy decisions applicable to a user within an IP Multimedia Subsystem, the apparatus comprising: a processor configured to: identify a group of which the user is a member; generate a request for policies and dynamic data stored in a Group Document of the identified group; a transmitter configured to send the request to a Group XML Document Management Server (XDMS); a receiver configured to receive a response from the Group XDMS, the response including the policies and dynamic data stored in the Group Document of the identified group, wherein the policies of the response includes policies that are applicable to the group as determined by combining policies of related groups identified within the Group Document with a users' group of the Group Document, wherein the combining policies with the policies of the identified related groups comprises any of: if a policy of the user's group contradicts a corresponding policy of a superior one of the identified related groups, overriding the policy of the user's group with the policy of the superior related group; and if a policy included in the user's group is narrower than a corresponding policy of a one of the identified related groups, overriding the policy of the superior related group with the policy of the user's group; wherein the policies comprise a maximum number of session in which members of the group are allowed to participate simultaneously; wherein the dynamic data comprises the number of sessions in which members of the group are participating; the processor is further configured to evaluate the policies using the dynamic data in order to make policy decisions. 20. The apparatus of claim 18 : wherein the processor is further configured to, based on the results of the policy decisions, generate a message for updating the dynamic data of the group; wherein the transmitter is further configured to send the message to the Group XDMS.