The information of the Server will be extended by other parts of this series of standards, by companion specifications or by Server vendors. There are preferred ways to provide the additional information.
Do not subtype DataTypes to provide additional information about the Server. Clients might not be able to read those new defined DataTypes and are not able to get the information, including the basic information. If information is added by several sources, the DataType hierarchy may be difficult to maintain. Note that this rule applies to the information about the Server; in other scenarios this may be a useful way to add information.
Add Objects containing Variables or add Variables to the Objects defined in this part. If, for example, additional diagnostic information per subscription is needed, add a new Variable containing in array with an entry per subscription in the same places that the SubscriptionDiagnosticsArray is used.
Use subtypes of the ServerVendorCapabilityType to add information about the server-specific capabilities on the ServerCapabilities Objects. Because this extensibility point is already defined in this part, clients will look there for additional information.
Use a subtype of the VendorServerInfoType to add server-specific information. Because an Object of this type is already defined in this part, clients will look there for server-specific information.