Halliday & Matthiessen (2014: 290):
In the ‘attributive’ mode, the circumstantial element is an attribute that is being ascribed to some entity … These take two forms:
(a) one in which the circumstance is construed in the form of the Attribute …
(b) the other in which the circumstantial relation is construed in the form of the Process …
In the first case, the circumstantial relation is construed as a minor process realised by a preposition; in the second, it is construed as a process realised by a verb …