Existential Processes: Between The Relational And The Material

Halliday & Matthiessen (1999: 514):

Finally, there is the phenomenon of existing — still construed, grammatically, as a type of process. What is said to exist may be an entity, something that persists through time, like there's a letter for you; but it may also, in many languages, be a happening, as in there was a fight. Here we have something that could alternatively be construed as a material process (people were fighting ), which suggests that "existential" processes are another intermediate type, something between the relational and the material.