The `Next' button leads to the immediately following page;
The `Up' button goes back up to the start page of the
current section or subsection (i.e., the next higher logical
unit of the document);
The `Previous' button returns to the immediately
preceeding page;
The grayed-out versions of these icons indicate that the corresponding
functions are not applicable in the given context;
The `Contents' button exposes the detailed table of
contents;
The `Search' button jumps to the search interface
(see also below);
The `Help' button leads to this section;
The `LIDOS button goes back to the LIDOS main page;
The `DFKI' button brings up the main Web page of the German
Research Center for Artificial Intelligence.