Do you mean by not changed:
1. That the value stays the same but timestamp changes
2. That both value and timestamp stays the same

In case of 1, you need to use a DataChangeFilter with trigger STATUS_VALUE_TIMESTAMP (i.e. DataChangeTrigger.StatusValueTimestamp), because the default behaviour without any filters is the STATUS_VALUE, i.e. no notifications if only the timestamp changes (see Part 4, Table 130 of the spec). In case of 2, there is no way to get notifications since nothing changes. Anyway extending the filter is meant for “specification level” extension, i.e. something both the client and the server should knowof.

There is a keepalive notification, which does not contain any notifications. This is sent whenever there has not been anything other to send for MaxKeepAliveCount of PublishIntervals. You can add a listener for these events, Subscription.addAliveListener. Also you might want to read spec Part 4: 5.13.1 on how the subscription model works.

For the BTW part, I need a bit more information. The only thing that should be a direct result of a browse is the increase in the Objects/Server/ServerDiagnostics/(uri of the session)/SessionDiagnostics/BrowseCount and that with diagnostics on.

– Bjarne