We need to think about the general 'feature' of syncing server cache (last value in MonitoredItem) and client cache.

If there is no retransmission, we need the ResendData method instead. But the profile that allows no queue does not require ResendData.

If we allow this we need to define how a client can resync.

5.13 Subscription Service Set
5.13.1.1 Description
Replace i) with the following text:
Sessions maintain a retransmission queue of sent NotificationMessages. NotificationMessages are retained in this queue until they are acknowledged. The Session shall maintain a retransmission queue size of at least two times the number of Publish requests per Session the Server supports. A Profile in OPC 10000-7 may make the retransmission queue support optional. The minimum number of Publish requests per Session the Server shall support is defined in OPC 10000-7. Clients are required to acknowledge NotificationMessages as they are received if the Publish response parameter availableSquenceNumber is not an empty array. An empty array in availableSquenceNumber indicates that the Server does not support a retransmission queue and acknowledgemet of NotificationMessages. In the case of a retransmission queue overflow, the oldest sent NotificationMessage gets deleted. If a Subscription is transferred to another Session, the queued NotificationMessages for this Subscription are moved from the old to the new Session.

5.13.5 Publish

Table 95 – Publish Service Parameters
Replace availableSequenceNumbers description with the following text:
A list of sequence number ranges that identify unacknowledged NotificationMessages that are available for retransmission from the Subscription’s retransmission queue including the sequence number of this response if it is not a keep-alive Message. This list is prepared after processing the acknowledgements in the request (see 7.8 for Counter definition).
The list shall be empty if the Server does not support the retransmission queue. If the list is empty, the Client should not acknowledge sequence numbers.

Table 97 – Publish Operation Level Result Codes
Add status code to table
Good_RetransmissionQueueNotSupported
The Server does not support retransmission queue and acknowledgement of sequence numbers is not available.

Updated in OPC 10000-4 - UA Specification Part 4 - Services 1.05.0 Draft11.docx
Errata is prepared

Agreed to changes edited in Virtual F2F including 1.04 and 1.03 Errata.