Optimization in graphs with bounded treewidth

Courcelle's theorem speaks about computational complexity of decision problems defined by formulae in monadic second order logic over relational structures with bounded treewodth. For a fixed treewidth and a fixed formula, Courcelle's theorem gives an algorithm, which decides the formula over a structure of said treewidth in linear time. is thesis provides a self-contained proof of Courcelle's theorem using methods of finite model theory. Furthermore it contains the proofs of all propositions and theorems upon which the main proof depends, notably the Ehrenfeucht-Fraïssé theorem widely used in finite model theory. e thesis also contains an implementa- tion of an algorithm which follows from the main proof. Finally a sketch of the current state of the art of the area of research is given, as well as the possibilities following from it.