The DDS.DataTagQosPolicy can be used to associate a set of tags in the form of (name, value) pairs with a DDS.DataReader or DDS.DataWriter. This is similar to the DDS.PropertyQosPolicy, except you cannot select whether or not a particular pair should be propagated (included in the built-in topic). Data tags are always propagated. The Access Control plugin may use the tags to determine publish and subscribe permissions.