Clarify: 'acl' rel link is a naming hint, not always points to existing file

[dmitrizagidulin]

Add an explanation to the ACL Resource Discovery section that the rel="acl" link will be returned even if no actual individual .acl file is present. That is, it's a naming hint, and not necessarily a link to an existing ACL resource.

[Otto-AA]

From my interpretation "a client can discover the location of its corresponding ACL" indicates that the ACL file actually has to exist if the link value is present. Therefore I would also welcome clarification on that.

[dmitrizagidulin]

@Otto-AA Yeah, exactly, the spec wording sort of implies that the file exists.
Whereas that's not the case, it's more like "if it were to exist, this is what it would be" -- it's most often just a naming hint.

[csarven]

https://datatracker.ietf.org/doc/html/rfc8288#section-2.1 :

[Link Relation Types by definition] only describe how the
current context is related to another resource.

Closing this issue as consensus is deemed to be captured in WAC Editor's Draft: https://solid.github.io/web-access-control-spec/ . https://solid.github.io/web-access-control-spec/#acl-resources details ACL resource discovery and representation, and there is no requirement that an ACL resource needs to have a representation. https://solid.github.io/web-access-control-spec/#effective-acl-resource-algorithm includes the case where an ACL resource may not have a representation.