UA Server Namespace table indices may vary over time. This represents a problem for those A&E COM Clients which cache and reuse fully qualified area names. One solution to this problem would be to use a qualified name syntax which includes the complete URIs for all referenced table indices. This however would result in fully qualified area names which are unwieldy and impractical for use by A&E COM Clients. As an alternative, the A&E COM UA Proxy will maintain an internal copy of the UA A & C Server's namespace table together with the locally cached endpoint description. The A&E COM UA Proxy will evaluate the UA A & C Server’s namespace table at connect time against the cached copy and automatically handle any re-mapping of indices if required. The A&E COM Client can continue to present cached fully qualified area names for filter purposes and the A&E COM UA Proxy will ensure these names continue to reference the same notifier Node even if the Server's namespace table changes over time.

To implement the relative path, the A&E COM UA Proxy maintains a stack of INode interfaces of all the Nodes browsed leading to the current level. When the A&E COM Client calls GetQualifiedAreaName, the A&E COM UA Proxy first validates that the area name provided is a valid area at the current level. Then looping through the stack, the A&E COM UA Proxy builds the relative path. Using the browse name of each Node, the A&E COM UA Proxy constructs the translated name as follows:

QualifiedName translatedName = new QualifiedName(Name,(ushort) ServerMappingTable[NamespaceIndex]) where

Name – the unqualified browse name of the Node

NamespaceIndex – the Server index

the ServerMappingTable provides the Client namespace index that corresponds to the Server index.

A ‘/’ is appended to the translated name and the A&E COM UA Proxy continues to loop through the stack until the relative path is fully constructed.