I am trying to do a similar thing (find the parent nodes of a given node). I have tried this:

UaNode node = uaClient.getAddressSpace().getNode(nodeId);
UaReference[] parentReferences = node.getReferences(Identifiers.HasComponent, true);

However, the UaReference array is always empty, and I know the node has a parent.

I also tried this (as mentioned in https://forum.prosysopc.com/forum/opc-ua-java-sdk/get-browse-path-by-nodeid/):

UaReference[] parentReferences = node.getReferences(Identifiers.HierarchicalReferences, true);

But the same, the array is empty.

Thanks for your reply.

The OPC server type we are most likely to connect to is Kepware, but it could be any other type too.

In my application I am dealing only with FolderType nodes which may have one or more Folder or Variable types as child components.

I’m using the Prosys OPC UA Browser app as a tool whilst working on this.

In the Reference section the Folders have:
HasTypeDefinition: FolderType
Organizes (x N): Other sub-folders
HasComponent (x N): Variables in this particular folder

In the Reference section the Variables have:
HasTypeDefinition: BaseVariableType

All of the references above are in the Forward direction. If I change the Browser direction to ‘Inverse’ then I get ‘No content in table’ for the both Folders and Variables alike.

The aim of the module I’m writing is that if I am passed a NodeId, to be able to construct the ‘Folder browse path’ to it. I understand that a Node might have several ‘parents’, but in this application it will be 99/100 that there will only be one ‘parent’ reference. If there is more than one then I will simply indicate that.

It looks like the Kepware server does not supply the Inverse references hence explaining why the array is empty – is my understanding correct? Does that mean that with this particular OPC server (Kepware), it is not possible to browse in the Inverse direction? If that is the case is there any way to implement what I am trying to achieve?

Thanks

Thanks for the suggestions, it is all making more sense now.

I checked with the UA Expert browser, and it is the same, so it looks like Inverse references are not supported/provided by the Kepware server I am testing on.

My application has to support a variety of OPC server types, so we cannot rely on special configurations, and as you say the requirement for Inverse references seems to be optional anyway, and therefore cannot be relied on.

I think maybe the only way to acheive this would be some kind of browse tree generator that runs in the background and caches the paths to the nodes. As it does not appear to be a trivial task and is ‘expensive’, it may be that we decide not to try to implement it anyway, as it was more of a ‘nice to have’ feature rather than a necessity.