An aggregating Server or GDS, needs to be able to discover the Servers that support AliasNames. Furthermore, the aggregating Server or GDS needs to be able to detect if a Server that contains AliasNames has had updates to the AliasName definitions. An aggregating Server or GDS could Subscribe for the LastChange Variable on AliasNameCategoryType instances to detect when a value is changed, but for systems with a large number of Servers the ClientServer connection might be difficult to manage. This section describes an extension for determining that a Server has had updates to the AliasName definitions. This extension to a Server that supports AliasNames, provides a Publisher capability for the Server (see OPC 10000-14). This extension also provides a simple way to determine if a Server has stopped or started.