If a particular repository restricts the read access of a particular user (see 6.9 Access Control), then the nodes and properties to which that user does not have read access will simply not appear to exist. For example, the nodes returned on N.getNodes will not include subnodes of N to which the user in question does not have read access. In other words lack of read access to an item blocks access to both information about the content of that item and information about the existence of the item.