hi,
we just kicking start a new open source ruby project "mojar workflow".
we named it after our deshi word "mojar" reason is very clear to
spread out this word.

mojar workflow, is integral solution to execute a flow of business
rules. for example -

you have an action where you have the following set of rules -
1. start transaction
2. verify user account
3. verify user balance
4. verify user dues
5. reduce dues from balance
6. complete transaction

after few days you got a new requirement, where you suppose to reduce
user dues by the 10% because of company new discount policy.
so you have to implement the following rules -
1. start transaction
2. verify user account
3. verify user balance
4. verify user dues
5. reduce dues by 10% of discount
5. reduce discounted dues from balance
6. complete transaction

to implement such scenario you have to again code in your stable
release. but using mojar workflow, you can add that new concern from
the abstract flow maintenance layer. where you can define this flow in
yaml file or an xml document.

keep your eyes on -
http://rubyforge.org/projects/mojarworkflow/

best wishes,