The three subdivisions of semiotics, the theory of signs, were defined by Morris as:
A more general view was taken by Carnap, who maintained that syntax is contained by semantics, and semantics is contained by pragmatics:
syntax 
semantics pragmatics
Perhaps more common is the view that to describe pragmatics, one must describe semantics, and to describe semantics one must describe syntax:
syntax 
semantics pragmatics
Or even vice versa:
pragmatics semantics syntax
But a more plausible view is to assume that each of these dimensions of signs is mutually dependent.