Halliday & Matthiessen (2014: 291):
Here the Attribute is realised by a nominal group and the circumstantial relation is expressed by the lexical verb in the verbal group serving as Process … The verb expresses a circumstantial relation such as ‘be + matter’, ‘be + extent in time’, ‘be + extent in space’. Being attributive, these are non-reversible; there are no ‘receptive’ equivalents …