A qualified single term presents an object or agent in a specified activity or circumstance. A composite term presents several interrelated elements whose combined arrangement is essential to the resemblance.
Examples:
“A person writing on water” — one agent in a particular futile action.
“A cloud of dust, flashes of swords above it, and the spatial relationship between them” — several elements forming an integrated scene.
The diagnostic question is whether attention falls on one object under a condition or on the configuration produced by several coordinated elements. A phrase is not composite merely because it has several nouns.