Halliday & Matthiessen (2014: 380-1):
We can now follow the experiential pattern that is embodied in nominal group structure. Proceeding from left to right, we begin with the immediate context, the identification of the item in terms of the here-&-now, e.g. those trains ‘the trains you can see over there’. Of course, this identification is often in terms of the surrounding text rather than the situation, e.g. those trains ‘the trains you’ve just been talking about’; but the point of reference is still the speech event.
From there we go on to quantitative features: place in order, and number. These are less naturally definitive than this or that, mine or yours, but more so than a merely qualitative attribute; and the ordinals, being the more definitive of the two, come first. An ordinal is a kind of superlative cardinal: third = ‘three-est’, i.e. identified by being at number three.
Next come the qualitative features, again with superlatives preceding others: the oldest trains ‘trains for which oldness is the identifying feature’. Often there is an intensifier, such as very, or an attitudinal element like nice, terrible as a marker of the quality.
Finally, comes class membership; this reduces the size of the total set referred to in the noun by specifying a sub-set, e.g. passenger train ‘kind of train that is for carrying passengers’.
We are talking here, it should be made clear, of the identifying potential of these elements. In any actual instance, the item in question may or may not be identifying; and this is the function of the word the at the beginning of the group – to signal that something that is capable of identifying is actually functioning in this way.
So there is a progression in the nominal group from the kind of element that has the greatest specifying potential to that which has the least;