Developing and maintaining a medium sized program is definitely facilitated by adopting a style of programming that has been introduced by  [Kn83] as literate programming. Apart from making a pun at the school of structured programming  [Kn83] professes the advantage of writing a program like one writes an article. As not to be trapped in yet another ideological debate we merely wish to state that we took pleasure in structuring a program as a document and mixing in explaining text. Before we start the description of our prototype implementation we wish to introduce some additional features of the DLP system. .so ext mod $=