Hello,

I have 4 questions regarding DataItem subscription (with Java OPC UA Server SDK) :

1) Is it possible to be notified when the source or server timestamp of the value is modified ? Even if the value itself remains the same ? My guess is that it’s not, but is there any way to do this ?

2) Is there a way to subscribe to an object and be notified if any of its variable changes ? My guess is that it’s not possible and that you can only subscribe to variables/properties directly, right ?

3) There is a function to transfer a subscription to another client in the SDK. Imagine that the subscription is transfered to a new client after the detection that a “master client” is disconnected. There will be a little time during which the server will be storing the notifications that the client missed, but when a new client gets the subscription, does it first start with a full notification of all the items (like the first notification of a new subscription) or only with the “partial” notification that were being stored for the first client ?

I would like my backup client to be able to perform its job as if it was the master client, ie: having the state of all the items of the subscription at the time of the master client failure + then the partial notifications that the master missed. If I do first a manual read in the backup client when the master fails, I may have missed some data changes between the disconnection of the “master client” and the transfer to the backup client.

So if 1 2 and 3 are not possible, I imagine that my solution could be to create a DataType containing all I need to know “together”, and be notified of the whole value if one of its property changes. Example : A value of MyDataType composed of informations A B C, if A B or C changes I get the value change notification containing A B and C. But I imagine 2 ways to do this :
4.a) If I create a DataType composed of several variables (like it seems to be the case for the standard “SessionDiagnostics” DataType), if I subscribe to a SessionDiagnostic item, am I notified if a subvariable changes ? If it works, can this data type be created directly by using UaModeler and the code generation or do I need to create the serialize/deserializer like in 4.b ?

4.b) If i create my own ComplexDataType from scratch (with a serializer and deserializer), then I think that if I modify anything in it I will be notified right ?

Thank you