Halliday & Matthiessen (1999: 223):
Since projection and expansion operate across the various categories of phenomena, we referred to them as transphenomenal categories. As transphenomenal categories, they are meaning types that are in some sense “meta” to the organisation of the ideation base: they are principles of construing our experience of the world that generate identical patterns of semantic organisation which are of variable magnitude and which occur in variable semantic environments. Such patterns therefore constitute fractal types.