7.7.1 | It is not recommended that institutions use spreadsheet tools for the usage of material models and the production of metrics used for regular decision-making. More robust systems are preferred. Nevertheless, if spreadsheets are the only possible modelling environment available initially, the standards in 7.7.2 must apply, at a minimum. |
7.7.2 | Spreadsheet implementation should follow a quality standard as follows: |
| (i) | The spreadsheet should be constructed with a logical flow, |
| (ii) | Formulae should be easily traceable, |
| (iii) | Formulae should be short and constructed in a way that they are easily interpreted. It is recommended to split long formula into separate components, |
| (iv) | Tables should include titles, units and comments, |
| (v) | Inputs should not be scattered across the sheets but they should be grouped in one worksheet/table, |
| (vi) | Hardcoded entries (i.e. fixed inputs) should be clearly identified, |
| (vii) | Tabs should be clean, i.e. when the implementation is completed, all work in progress should be removed, |
| (viii) | Instructions should be included in one or several tabs, and |
| (ix) | Wherever suitable, cells should be locked and worksheets protected, preferably by password. |
7.7.3 | Models implemented in spreadsheets that deviate from the above criteria must not be employed for regular production. |
7.7.4 | To ensure their robust implementation, spreadsheet tools must include consistency checks. Common consistency checks include: (i) computing the same results through different methods, (ii) ensuring that a specific set of inputs leads to the correct expected output values, and (iii) ensuring that the sensitivities of outputs to changes in inputs are matching expected values. |
7.7.5 | If an institution employ spreadsheets for regular production, a rigorous maker-checker process must be implemented and documented. The review of spreadsheet tools must be included in the scope of the independent validation process. In addition, a clear version control should be implemented. |