These are the definitions of the types of formulas available within Rulestream
Fired only if its result becomes dirty/invalidated/de-cached (and fired only when its result is demanded). It gets dirty/invalidated/de-cached when another rule that it depends on gets invalidated.
A manual override of a result will invalidate all results that depend on it. A manual override to a standard result will stop the rule from firing until the manual override value is explicitly thrown away and the result reverted to rule formula. If the result is not invalidated it returns the cached value when asked.
Fired similar to a standard rule, however the manual value is automatically thrown away if any of the other results that it depends on are invalidated. In other words, the manual override does not stop the rule from firing (as it does for a Standard rule).
Fired only the first time it is demanded after which the value is cached and never re-evaluated.
Follow Part Number:
A follow part number rule is kept in sync for all parts that have the same part number. A change in result of one part will cause the result to change for all parts with the same part number.