Clients use the browse Services of the View Service Set to navigate through the AddressSpace to discover the HistoricalNodes and their characteristics. These Services provide the most current information about the AddressSpace. It is possible and probable that the AddressSpace of a Server will change over time (i.e. TypeDefinitions may change; NodeIds may be modified, added or deleted).

Server developers and administrators need to be aware that modifying the AddressSpace may impact a Client’s ability to access historical information. If the history for a HistoricalDataNodes is still required, but the HistoricalDataNodes is no longer historized, then the Object should be maintained in the AddressSpace, with the appropriate AccessLevel Attribute and Historizing Attribute settings (see OPC 10000-3 for details on access levels).

If the HistoricalConfiguration of a HistoricalDataNode in the AddressSpace is changed and audit events are supported, an audit Event of AuditHistoryConfigurationChangeEventType shall be generated.

A Historian shall expose the Historizing attribute on any nodes that are currently collecting historical data. They shall also set the AccessLevel HistoryRead and optionally the HistoryWrite bits for HistoricalNodes (those with Historical data).

If a HistoricalConfiguration Object is added to or deleted from a Server or a Reference to a HistoricalConfiguration Object is added to or deleted from a Node, a GeneralModelChangeEvent shall be generated. If an Annotation Property is added to or deleted from a Node, a GeneralModelChangeEvent shall be generated.