(Note: I'm not advocating this approach, I merely repeat what I think I know) Instead of hard coding the subject hierarchy in templates (like "/topic/subtopic/

(Note: I'm not advocating this approach, I merely repeat what I think I know) Instead of hard coding the subject hierarchy in templates (like "/topic/subtopic/"), you define a document type that exposes target elements as links (typically with a "rel" attribute identifying the type of element). The client can then navigate the logical hierarchy without requiring this to match the physical URLs (think: federation across departments; instead of having a template "/api/{department_id}/people/{employee_id}", the company can expose a directory document that aggregates links "link rel='employee' target='https://departmentX.company.com/arbitrary/hierarchy/employees/12345'" https://departmentX.company.com/arbitrary/hierarchy/employee... and "link rel='employee' target='https://othercompany.com/api/users/Doe+John'" https://othercompany.com/api/users/Doe+John'"). The type of linked resources must of course be aligned; there's no magic involved. Instead of the client having out-of-band knowledge about the hierarchy, the client must have out-of-band knowledge about the used document types containing the links.