foo is not a valid UUID

Value is not a valid UUID, as defined by RFC 4122.

Ensure that the UUID id is permanent, universally unique and consists of 8 hex digits followed by a dash followed by 4 hex digits followed by a dash followed by 4 hex digits followed by a dash followed by 12 hex digits.

Other alternatives:

• If your alternate link is a a permalink, simply use the same value as the id for the entry.

• Use a 'tag' URI instead, as described here.