"Expenditure" refers to the expenditure history. The so-called "overhead" means "fictional history that didn't really happen", including historical background and future. The biggest difference between novels is that stories usually take place in the history or future that the author fictionalizes or adapts based on certain creative premises (such as entertainment and specific background), and in a world that the author randomly sets. Generally speaking, overhead historical novels are full of fantasy colors.
Overhead technique is usually used in sci-fi future novels or some novels set in ancient society. Novels with modern life as the theme are mostly fictional, but they are not classified as empty novels because they describe the current social life and have unique relativity.
Novel classification
All overhead: it means that the characters, environment and specific events in the novel are all made up by the author's subjective imagination and have never really existed. Science fiction is mostly air fiction, such as Three-body and Space Overture.
Some novels set in ancient society also advocate overhead techniques, and their overhead social forms and social rules often allude to or virtualize a certain era in history, but this virtual era itself has never existed, so it is still completely overhead. For example, the chronicles of Narnia and The Lord of the Rings.
Half-empty: refers to the characters, environment and specific events in the novel unfold in the form of half truth and half falsehood, or the virtual is greater than the real, and the virtual is greater than the real. When writing, it is common to keep the background, characters and events of a real event in history, and then add virtual characters, such as Walking on Thin Ice and Beautiful Mountains and Rivers.