Relationship values can be used in principle for document specific toolbars/menus when used with the link element in document head e.g. start, contents, previous, next, index, end, help to link to a separate style sheet (rel="stylesheet") to make a link to a script (rel="script") by stylesheets to control how collections of html nodes are rendered into printed documents to make a link to a printable version of this document e.g. a PostScript or PDF version (rel="alternate" media="print")