Topics are defined with a privacy level that defines what level of de-identification is required for a subscriber to receive a publication for that topic. Publishers and subscribers are only shown (and only able to create) topics that meet the privacy level they are assigned. The privacy level an organization is assigned is determined during the registration process of an organization. The set of available privacy levels are established at the organization level. A gateway can only support a privacy level if that level is supported by its associated organization. Each privacy level is independent of any other. Although privacy levels might seem hierarchical in nature (with one privacy level providing more restrictive data access than the previous), privacy levels in no way inherit characteristics from other privacy levels. Although the default privacy levels in HCN refer to specific provisions of United States laws that are related to healthcare information security, privacy levels are completely customizable and can be tailored to any national, regional, or private security regulations. For information about how to customize privacy levels, see Appendix A, "Customizing Healthcare Collaborative Network" on page 181. For further details on privacy within HCN, refer to Chapter 6, "Privacy and security" on page 165.