Architecture discussion

I am new in ROR . I need to design my ROR web application that support
distribute environment(different client like web client and mobile
client). I struck with the MVC model of ROR as i am J2EE developer. I
want to separate my Navigation logic ,Business logic and Database
logic. But rail archtecture provide me only controller and Model. if i
put my BL in controller or BL in model i am not able to seperate my
BL. I want to implement service base concept while designing my

Can you please provide your valuable suggestion. How i separate my
Business logic in ROR architecture in order to achieve reusable