There is no way specified for upward navigation.

Currently there is no way specified for upward navigation. i.e.

1. knowing parent container of given resource.
2. knowing subject resource of given auxiliary resource.

Uri semantics are necessary and not sufficient for case 1. i.e. they specify that a containment statement must satisfy hierarchical naming constraints, but hierarchical name is not sufficient to derive containment statement. So if a resource uri is a/b/c.acl, it doesn't encode fact <a/b/> ldp::contains <a/b/c.acl>.

This lack of navigability implies, we cannot provide any context if user directly landed at a resource representation. It is like, they bookmarked a file, and their file manager says it can only "best guess" it's parent directory.

Currently downward navigation is provided for two classes of relation

1. Containment downward navigation is accounted through containment statements in container representation.
2. Auxiliary downward navigation is accounted through link headers of subject resource get/head response.

For upward navigation, no mechanism. One proposal is to have entire provenance chain in single auxiliary resource as described in issue #399. If it is not viable, at least one reverse link header will help.

No implementation files or tests are named. Start by reading issue #399 and the existing specification sections describing containment statements and Link headers for downward navigation. Done means documenting and agreeing on a mechanism for both parent-container and subject-resource upward navigation, including the reverse-link behavior.