- We want: representation of ``real'' distribution of (, , ) by finite set of numbers
- We need: restriction: transformation continuous values discrete representation
- We need: reconstruction: transformation discrete representation continuous values
- We get: hints for the discretization of the spatial and temporal operators

Concepts of ``restriction'' and ``reconstruction'' are often used during the construction or analysis of a numerical scheme.

These concepts might not show up in the actual algorithm: different concepts may result in the very same scheme.