Deep structure is a level of syntactic representation in generative grammar that has four key properties: it defines major grammatical relations, all lexical insertion occurs at this level, all transformations occur after it, and semantic interpretation occurs at this level. There was significant debate following the publication of Aspects of the Theory of Syntax in 1965 around whether there is a single level of representation that possesses all four of these properties. Part of this debate focused on whether transformations preserve meaning and whether sentences that appear different on the surface, like active vs passive vs imperative, are derived from the same underlying deep structure.

1. Properties of Deep Structure
"Deep structure is a level of syntactic representation with a number of
properties that need not necessarily go together. Four important properties of
deep structure are:
1. Major grammatical relations, such as subject of and object of, are
defined at deep structure.
2. All lexical insertion occurs at deep structure.
3. All transformations occur after deep structure.
4. Semantic interpretation occurs at deep structure.
"The question of whether there is a single level of representation with these
properties was the most debated question in generative grammar following the
publication of "Aspects [of the Theory of Syntax" 1965]. One part of the debate
focused on whether transformations preserve meaning."
The first sentence is active, secondis passive, and the last is imperative. However, if youtake a
look those closely, youwillfind that those three are very closely related, evenidentical. They
seem to be identical, since they have the same underlyingabstract representationthat is
called deep structure.
e.g.
The DS (deep structure)
SD (structure description) :
SC (Structuralchange) :
SS (Surface structure) :
1 2 3 4
3 4 + be 2+en 1
The door is closed
by you
Note: the SC is passive transformationrules
(3) SD:
SC:
SS:
1 2 3 4
0 2 3 4
Close the door!
Note: 0 is deletion