Note that absolutely qualified identifiers are much less prevalent with the advent of Unison projects. They refer to a term from the root of the entire codebase, not the root of a particular project, so their usage is limited to legacy support of a pre-project era.
Namespace-qualified identifiers are relative to a “current” namespace, which the programmer can set (and defaults to the root of the current project). To ignore the current namespace, an identifier can have an absolute qualifier. An absolutely qualified name begins with a .. For example, the name .base.List always refers to the name .base.List, regardless of the current project or namespace, whereas the name base.List will refer to lib.base.List if the current namespace contains the base library in its lib namespace.