DirectoryType is the ObjectType for the root of the GlobalDiscoveryServer AddressSpace. It organizes the information that can be accessed into subfolders It also provides methods that allow applications to register or find applications. It is defined in Table 3.
Table 3 – DirectoryType Definition
|Namespace||GDS (see 3.3)|
Subtype of the FolderType defined in OPC 10000-5.
|HasComponent||Method||FindApplications||Defined in 6.3.4.||Mandatory|
|HasComponent||Method||RegisterApplication||Defined in 6.3.6.||Mandatory|
|HasComponent||Method||UpdateApplication||Defined in 6.3.7.||Mandatory|
|HasComponent||Method||UnregisterApplication||Defined in 6.3.8.||Mandatory|
|HasComponent||Method||GetApplication||Defined in 6.3.9.||Mandatory|
|HasComponent||Method||QueryApplications||Defined in 6.3.10.||Mandatory|
|HasComponent||Method||QueryServers||Defined in 6.3.11.||Mandatory|
The Applications folder may contain Objects representing the Applications known to the GDS. These Objects may be organized into subfolders as determined by the GDS. Some characteristics for organizing applications are the networks, the physical location, or the supported profiles. The QueryServers Method can be used to search for OPC UA Applications based on various criteria.
A GDS is not required to expose its Applications as browsable Objects in its AddressSpace, however, each Application shall have a unique NodeId which can be passed to Methods used to administer the GDS.
The FindApplications Method returns the Applications associated with an ApplicationUri. It can be called by any Client application.
The RegisterApplication Method is used to add a new Application to the GDS. It requires administrative privileges.
The UpdateApplication Method is used to update an existing Application in the GDS. It requires administrative privileges.
The UnregisterApplication Method is used to remove an Application from the GDS. It requires administrative privileges.
The QueryApplications Method is used to find Client or Server applications that meet the criteria provided. This Method replaces the QueryServers Method.
The QueryServers Method is used to find Servers that meet the criteria specified. It can be called by any Client application. This Method has been replaced by the QueryApplications Method