  Among the multiple causes of high error rates in spreadsheets, lack of proper
training and of deep understanding of the computational model upon which
spreadsheet computations rest might not be the least issue. The paper addresses
this problem by presenting a didactical model focussing on cell interaction,
thus exceeding the atomicity of cell computations. The approach is motivated by
an investigation how different spreadsheet systems handle certain computational
issues implied from moving cells, copy-paste operations, or recursion.
