Major change Change involving restructuring (chapter 4 was split up) and additional subsections Due to this restructuring, the files program_code.tex and program_tools.tex were renamed and furthermore, osl.tex was split up; besides this, there were only slight changes - as regards content, only one short paragraph is added (to impl_code.tex). Much new content is added in Chapter 2 and Chapter 3. Bibliography was changed and extended.