  This paper presents a toolkit for spreadsheet visualization based on logical
areas, semantic classes and data modules. Logical areas, semantic classes and
data modules are abstract representations of spreadsheet programs that are
meant to reduce the auditing and comprehension effort, especially for large and
regular spreadsheets. The toolkit is integrated as a plug-in in the Gnumeric
spreadsheet system for Linux. It can process large, industry scale spreadsheet
programs in reasonable time and is tightly integrated with its host spreadsheet
system. Users can generate hierarchical and graph-based representations of
their spreadsheets. This allows them to spot conceptual similarities in
different regions of the spreadsheet, that would otherwise not fit on a screen.
As it is assumed that the learning effort for effective use of such a tool
should be kept low, we aim for intuitive handling of most of the tool's
functions.
