I have read that story point estimation is not intended to actually tie with number of hours , but is used to identify the relative capacity. I have a java application which has a adapter layer , a service implementation layer , a DAO layer and an external connector service layer. If I am given a high level requirement , is it a good practice to a classification of story points for each layer - eg:Adapter : small : 1 SP , medium 3 SP , Large : 5 SP , Extra Large : 8 SPImpl : small : 3 SP , medium 5 SP , Large : 8 SP , Extra Large : 11 SPDAO : small : 1 SP , medium 3 SP , Large : 5 SP , Extra Large : 8 SPIs it a good way of estimation? Or should we always estimate by looking as application as whole for each change? For eg, If I have got 2 user stories , should I estimate size of user story as a whole , say 1 US takes up 5 SP and other takes 13 SP? Does component-wise breakdown make sense for story point estimation? 
Story Point Estimation - Component Based
requirements;estimation;user story