A Global Discovery Server (GDS) that supports AliasNames, provides AliasNames functionality, but the target Nodes referenced are in other Servers. The AliasNames are aggregated from the Servers that have registered with the GDS that expose the “Alias" capability (for information on capabilities see OPC 10000-12). Additional examples on aggregating AliasNames can be found in the aggregating Server example – A.3. A GDS implementation also requires additional behaviour. This section describes automatic behaviour that is required by all implementations of a GDS that supports AliasNames. An example of a GDS that supports AliasNames is illustrated in Figure B.1.

Figure B.1 – Example GDS aggregating AliasNames

The following sections describe this required behaviour:

• When a Server registers with the GDS, the GDS shall merge the AliasNames of the registering Server into a master AliasNames list on the GDS.
• Pull all AliasNameCategory instances, merge any that have identical Name part of the BrowseNames.
• The GDS will provide the ExpandedNodeId of all of the referenced NodeIds and the ServerUri of the Server containing the NodeId.

The details of the expected behaviour of a GDS that supports AliasNames is described inB.2, B.3 and B.4.