Disclaimer: I am not an academic linguistics scholar, so it’s very likely that my description of the idea of deep and surface structure contains errors at the detail level.
What’s more, Transformational Grammar has long been replaced by more recent theories in linguistics. Nevertheless, it was an input into NLP, and the high-level description given here will not let you down as far as applying NLP language patterns is concerned.
© 2020, Andy Smith. All rights reserved.