Isogeometric finite elements combine the numerical solution of partial
differential equations and the description of the computational domain
given by rational splines from computer aided geometric design. This
work gives a well-founded introduction to this topic and then extends
isogeometric finite elements by a local refinement technique, which is
essential for an efficient adaptive simulation. Thereby a hierarchical
approach is adapted to the numerical requirements and the relevant
theoretical properties of the basis are ensured. The computational
results suggest the increased efficiency and the potential of this local
refinement method.