Paul is now retired, but taught Decision Support Systems in the 80s and 90s. Initially students used IFPS (Interactive Financial Programming System, no longer in existence) but gradually he moved on to Lotus 123 and then Excel. The goal was not to teach Excel (as in what button is where) but rather how to use Excel.
The key idea of Paul is to separate designing the spreadsheet form making it. Do not immediately sit in front of the computer, model the domain first. Also, clearly understand and model the various variables: input, parameters, calculation and output.
Paul’s number 1 rule for modeling is: Keep your formulas simple: no more than 1 mathematical function per formula
Some people would model the costs like this:
But Paul’s approach is to split up the formula and model small steps. At Eusprig Paul will present a more elaborate approach for the modeling.
There are some open research questions here:
- Is it quicker to build a spreadsheet using a modeling approach?
- Are the resulting artefacts less error-prone?
- Are they easier to maintain, understand and to audit?