This may be just me not understanding it well, but here is the problem:

In 1.04 Part 5 Table 156 (ModelChangeStructureDataType Structure), we have ReferenceAdded and ReferenceDeleted verbs. The description of them both contains the text "The affected Node may be either a SourceNode or TargetNode.".
My problem is that this is too vague - for my use case, I think that I must know which of the two nodes it is. The description then proceeds with saying, for ReferenceAdded , "Note that an added bidirectional Reference is reflected by two changes." (and analogously for ReferenceDeleted).

Let's say I want to keep track on the client what are the forward references from Node1, so I would make a browse and store them, and subscribe to model change events. I would like to know when there can be a new or deleted forward reference from Node1. How can I do that? It seems to me that there is nothing in ModelChangeStructureDataType that allows me to detect the right event. What I am interested in are references added or deleted whose SourceNode is Node1 (and the TargetNode is irrelevant at that point). When such event occurs, I could re-browse Node1 to obtain the new set of references.

The way I read the spec, I may never receive such event, because if, let's say, a reference from Node1 to Node2 is added, the server may choose to set the affectedNode to TargetNode (Node2), and my code would not understand that this is a change that has anything to do with Node 1. For bidirectional references, the server will then send a second change, for the inverse reference. And it may choose to set the affectedNode to the SourceNode of the inverse reference, which would be Node2 again, so again my code would not detect this as being related to Node 1.

There is also a converse problem: If I am interested in forward references from Node1, for an added reference from Node0 to Node1 the server may choose to set affectedNode to TargetNode (Node1), and the client will be forced to rebrowse the Node1 even though it is not needed at that moment.

Note: Definitions of bidirectional/unidirectional are in 1.04 Part 3, 5.3.2. Attributes [of ReferenceType NodeClass].