Spreadsheet programs,  artifacts developed  by non-programmers,  are used  for a
variety of important tasks and  decisions. Yet a significant proportion  of them
have servere quality problems. This thesis presents a new approach for  checking
spreadsheets  on   the  premises   that  their   developers  are   not  software
professionals. The  approach takes  inherent characteristics  of spreadsheets as
well  as  the conceptual  models  of spreadsheet  programmers  into account  and
incorporates ideas from symbolic testing and interval analysis. 
Unlike   symbolic  testing,   which     requires    expressing    formulas    in
terms     of  input  variables,  interval-based    testing  uses    intermediate
variables    for   the  purpose  of    narrowing down   computed  intervals.  In
addition,  while  symbolic testing  is  used  to  validate  a  formula  for  any
possible  values of  the  input variables, interval-based testing   requires the
values  of  the variables    to be  expressed  as   intervals and   validity  is
determined  based  on the  intervals
provided.
The observation  that spreadsheets  are mainly  used for  numerical computations
enables us to introduce the idea  of interval analysis to spreadsheet   testing.
Intervalbased testing  focuses  on  the functionality  of  spreadsheet  formulas
instead of  the internal  structure of a spreadsheet  program (i.e.,  it is  not
based  on code  coverage criterion).  It requires the user to specify input  and
expected intervals for  desired input  and  formula  cells  respectively.   This
will  be   documented  in  a  behind-the-scene  spreadsheet and  used to perform
interval  computations  during  the verification  of  a  given spreadsheet.   In
addition,  the   expected  intervals  provided  by  the  user  are  verified for
reasonableness   using  interval  analysis.  The   approach  provided  is   thus
essentially  a   kind   of  stratified   plausibility   check  based   on    the
consistency of legitimate boundaries
users might specify for computations.