In repositories that have multiple workspaces, a node in one workspace may have corresponding nodes in other workspaces. A node's corresponding node is defined as follows:
A node's corresponding nodes are those with the same correspondence identifier.
The correspondence identifier of a referenceable node is its UUID.
The correspondence identifier of a non-referenceable node with at least one referenceable ancestor is the pair consisting of the UUID of its nearest referenceable ancestor and its relative path from that ancestor.
The correspondence identifier of a non-referenceable node with no referenceable ancestor is its absolute path.
Recall also that (as stated in 4.9 Referenceable Nodes) if a repository has a workspace with a referenceable root node then all its workspaces must have referenceable root nodes and those root nodes must all have the same UUID.
Apart from having the same correspondence identifier, corresponding nodes need have nothing else in common. They can have entirely different properties and child nodes, for example.
While a node may have a corresponding node in another workspace, it is not required to.
Note that there is still at most one node with a given UUID per workspace.
The update method,
Node.update(String srcWorkspace)
causes this node and its subtree to be replaced by a clone of this nodes corresponding node and its subtree in srcWorkspace.
For more details on corresponding nodes and the update method see 7.1.8 Updating and Cloning Nodes across Workspaces.