For some reason I cannot fathom, a complete description of Basis isn't in the doc...
PMF calculates Percent Reached for descending Meausres by dividing the Target into
the Actual value and multiplying the result by 100. If the descending Measure had a
Target of 0, this would have resulted in a Divide by Zero, which would have been
mathematically invalid. Special handling is therefore required for Measure Targets that
are set to zero.
In cases where you had a target of 1 or a fractional target, and an Actual that was many
multiples higher (e.g., a Target of .05 and an Actual of 25), you would see a seemingly
abnormally high Percent Reached (sometimes so high as to overflow and display *******
as the Percent Reached).
Basis controls where you would have zero Percent Reached. The basis is the point you
would exceed with your Descending Measure greater than which your Percent Reached
would start moving into the negative. Any Actuals that were greater would show a
negative Percent Reached; any that were less will show a positive Percent Reached.
Setting the Basis gives you control over how Percent Reached is calculated so you can
see more reasonable-looking Percents Reached.
How Descending Measure Basis Handling Works
The special handling lets you pick a defined numeric value as your zero crossing for
Percent Reached. The value can be sufficiently large that you would never exceed it, or
you can adjust it as needed until your numbers look reasonable.
If you set a Basis for a Descending Measure, the calculation for Percent Reached
subtracts the Actual from the Basis amount and the Target for the Basis amount, which
rebalances the Percent Reached to give you more control when Target numbers get very
What this means: If the target for your descending measure SUMS out to equal the basis exactly (and note that if your measure uses continuous rather than discrete values the odds of this are QUITE LOW), you would in concept hit a divide by zero but you never do, since we defend against divide by zero deterministically by setting set Pct Reached to 0 rather than having "undetermined value" for an answer (and/or having WebFOCUS throw an error halting processing).
Hope this helps.
Bob Jude Ferrante
Director of Business and Development
WebFOCUS Performance Management
I'll take any questions about PMF - business or technical - anytime!