This thesis introduces drawings, a class of mathematical structures suitable
to represent the syntactic structure of natural language sentences. Drawings
are simple structures, and independent of any grammar formalism or generating
device. The derived structures of many grammar formalisms can be interpreted
as a drawing. Structures derived by different formalisms can thus be compared
on a common base.
Drawings are not restricted to projective analyses. We present two measures
for the level of non-projectivity of drawings: gap degree and
well-nestedness. With these two measures we characterise the class of drawings
that corresponds to the derivations of Tree Adjoining Grammar (TAG).
Furthermore, a description language for well-nested drawings is presented and
complemented with an algorithm that enumerates all drawings for an expression
of that language.