I'm trying to build a OPC UA client application.
I'd like to be able to identify a UA node uniquely in the OPC tree.
I know that in OPC DA, a standard node id is a string with a '.' as a delimeter that I can use in order to identify a node.
In OPC UA, the node ID doesn't have to be a string, but I'd still like to be able to build a unique string that maps to a particular node.
I'm thinking about basing it on the the nodes names. e.g.: Demo.MyNode.MyValue.
but I'm afraid that the node name can contain characters such as "." and this will make my IDs not unique.
Is there a character I can use as a delimeter?
Is there a better way to represent the node ID as a string (including its path)?
OPC-UA offers the concept of a unique "BrowsePath" for each and every node, and a client could opt to store BrowsePaths instead of NodeIds, and then upon startup call the TranslateBrowsePathsToNodeIds service.
In fact, I believe this may be the intended behavior, as there's no requirement that a server use the same NodeId for any given Node after restarting, even if in practice that's how it's done.
I was wrong about NodeId being allowed to change. The spec says: "A Server shall persist the NodeId of a Node, that is, it shall not generate new NodeIds when rebooting."
I now believe its best to store NodeIds and only use BrowsePaths to aid in programming against type definitions.