Mathematical modeling plays an essential role in science and
engineering. Costly and time consuming experiments (if they can be done
at all) are replaced by computational analysis. In industry, commercial
codes are widely used. They are flexible and can be adjusted for solving
specific problems of interest. Solving large problems with tens or
hundreds of thousands unknowns becomes routine. The aim of analysis is
to predict the behavior of the engineering and physical reality usually
within the constraints of cost and time. Today, human cost and time are
more important than computer cost. This trend will continue in the
future. Agreement between computational results and reality is related
to two factors, namely mathematical formulation of the problems and the
accuracy of the numerical solution. The accuracy has to be understood in
the context of the aim of the analysis. A small error in an
inappropriate norm does not necessarily mean that the computed results
are usable for practical purposes.