IHE – XDS Notifications
IHE – XDS Notifications
The XDS notification functionality methods are:
Notification: The Notification of Document Availability (NAV) Profile is a little known supplement. It defines a simple XML encoded manifest of document references, and indicates to send this in an e-mail message. This is just a list of document ID values, so it is not exposing patient privacy in any direct way.
PUSH: That is to Push the content using XDR or XDM. This could be a copy of the documents, because they are globally uniquely identified there is no problem that they get duplicated.
Subscription: There is the Document Subscription (DSUB) profile that allows a system to ‘subscribe’ to be notified. This subscription contains a filter criteria that would constrain why a notification would happen. Although this is a rather technically easy profile, it is not implemented often. It is not clear how big does a notification system need to be to satisfy a growing population of systems that want notification. This profile is also tied to SOAP webservices, and really only works within a single XDS domain.
Atom Feed: This is really a polling query, but the results often is seen as a form of notification. The Atom feed is a part of the Mobile Health Documents (MHD) profile.
Is there a pattern that we don’t have? I know of some creative ways to use TCP sessions that are left in a closing state, where the one that knows who to notify closes the connection when there is something useful to pull, thus causing the system to poll only when this session close event happens. This is a very low overhead, but does require the systems handle many failure-modes robustly. This is what happens in some mobile APIs to help limit the polling traffic.
Specific to workflows, in the Cross-Enterprise Document Workflow (XDW) profile we did document that a workflow does need to have a system watching to make sure workflows do progress normally. This system could notice a workflow document that seems to have stalled, and give notice via a mechanism like NAV.
It seems we have plenty of ways to achieve the functionality. This technical solution should not be confused with what the user sees or feels.
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