Combinations that don't exist
An advanced technique: telling Axmo which combinations of elements cannot happen, so it neither calculates them nor accepts data there.
This is an advanced technique. You do not need it for your first models, and many models never need it at all. It helps when your business has combinations that cannot happen and you want the model to know that. Treat it as a way to refine a model you already have, not as a step in building one.
Not every combination is real
A model with a Product dimension and a Production stage dimension holds a cell for every product at every stage. In a real factory, some of those pairs never occur. A frying pan never goes through the welding stage. A plant may have no gas supply. A brand may not be sold in one country.
Without being told, Axmo treats every combination as possible. It calculates them all and accepts data for any of them. In a report, the impossible ones show as rows with nothing in them.
A rule says which combinations do not exist
A combination rule names combinations that do not exist. From then on, Axmo treats them as absent:
- They are not calculated. A formula that reads one finds an empty cell.
- Nothing can be loaded into them. If your data puts a value there, the Update stops. It names the rule, the series and the combination, so a mistake in the source data is caught instead of being added in quietly.
- Totals and split-downs leave them out. A value spread down from a total goes only to the combinations that exist.
- Reports leave them out. A row or column that cannot exist for any series it shows is not drawn.
Two ways to write one
As a list. You name the combinations, such as Italy × Nike. A total stands for everything beneath it, so Italy × All brands means every brand in Italy.
As a formula. A formula on your input data decides, combination by combination. In the Kitchenware example, a product passes a production stage only where it has a production time at that stage. One formula therefore removes every stage a product never visits, and stays right when the data changes.
Either kind can exclude the combinations it describes or include only those. Use whichever gives the shorter list.
Worth knowing
- A combination is gone if any rule removes it.
- A total disappears only when everything beneath it is removed.
- A formula rule reads input series only, never calculated ones.
- A rule applies to every series that has all of its dimensions, unless you leave some out.
- The dimensions themselves do not change: a rule removes combinations, never elements.
Where to find it
In the Dimensions editor, open the ⋯ menu in the left-hand list (after +Sequential) and choose Dimensional combinations. Press +Rule to start one. A rule takes effect when you save it, and after the next Update each rule shows how many combinations it removes.