Calculation blocks are the paragraph structure of the worksheet. Analogous to a paragraph communicating a single idea lead by a topic sentence, a prototypical calculation block contains a single calculation in its last row.
The other rows above this calculation contain the precedents to the calculation, each in turn a link directly to the source line item. These precedents, the ‘ingredients’ to the calculation, should include links to the source line item’s row label, so-called live labeling. They are separated by blank rows above and below to visually separate them from adjacent calculation blocks.
FAST 2.02-01 Construct all calculations in a separate calculation block
All ingredients must be presented as links immediately above the calculation with consistent calculation order and appearance in the formula.
FAST-2.02-01.1 except when the calculation block is a balance corkscrew
FAST-2.02-01.2 except when cascading calculations are warranted
FAST-2.02-01.3 except when the calculation is a trivial formula
FAST-2.02-01.4 except when a 2D line item is deemed the more efficient and/or readable design solution
FAST 2.02-02 Build calculation blocks so they can be replicated
Build calculation blocks so that they can be copied and re-used; apply minimum anchoring on formulas; row-anchor all links to facilitate re-using the structure.
FAST 2.02-03 List common calculation block components in a consistent order
Place oft used components (e.g. timing flags, indexation factors) in a similar position each time they are used, usually placing more significant commercial components first and timing flags and factors last.
FAST 2.02-04 List precedents in the order they appear in a formula
FAST-2.02-04.1 except when this violates a ‘pyramid’ layout
Maintain calculation order by listing precedents in the order they are used in the formula (except for priority for pyramid structure, i.e. where constants are listed first).
FAST 2.02-05 Use corkscrew calculation blocks for balance accumulation
Balance accumulations should be performed by a special calculation block referred to as a ‘corkscrew’, not via semi-anchored cumulative SUMs. A corkscrew can take one of three design forms:
• a 4-line corkscrew,
• 7-line corskcrews with flag, and
• 7-line corkscrew with PPF.
FAST 2.02-06 Use timing flag and factor components routinely
Use timing flags (or if required, partial period factors, a.k.a. PPFs) and separate indexation factors universally. Conditional logic embedded in complex formula to test for timing issues should never exist; separating this complexity from the primary calculation with timing flags or factors is always the preferred solution.
If there is a question of setting the time period or inflation that is not driven by flags and factors respectively, then the calculation block is likely poorly designed.
