Halliday & Matthiessen (2014: 561):
It is important to distinguish between an elaborating group and an embedded group occurring as Qualifier: e.g.
- (taxis, elaborating) his latest book, ‘The Jaws of Life’,
- (embedded) his book ‘The Jaws of Life’.
The former is related to a non-defining relative; it means ‘his latest book – which is “The Jaws of Life” ’, and is marked by tone concord://4 ^ his /latest /book the //4 jaws of /life was a //1 ghastly suc/cess //
The latter is related to a defining relative clause; it means ‘this particular book of his (he has written others)’ and has no tonic prominence on book.
Note that or in the sense of an alternative name for something is elaborating not extending; e.g.:In one of those cities – one [[ whose name has long been forgotten]] – there lived an old halac uinic, or chief.
I understand || that later, you come to an age of hope, or at least resignation.