We're running into issues where our facts are based on transactional access to a database. When we try to properly decompose our rules into multiple facts, we hit problems where the same transaction is trying to be used simultaneously because the rules engine appears to process facts in parallel by default.

I know there's a way to set priority on rules and facts which should make them run serially. The issue with this approach Is that is appears to be declarative on the fact itself and not on the user of the fact when constructing rule conditions. This makes it hard to use when you may want to decompose rule conditions in different order but still have them run serially instead of in parallel.