Why would someone using Core Data want to use more than one persistent store in the same Managed Object Model?

I'm pretty new to Core Data, and 开发者_运维技巧I'm trying to wrap my head around it.

You might have cases where you want different types of data stored in different places or with different behaviors. For example you might have one read only sqlite store shipped as part of your app containing some default data, an additional store for updates to that data set you have downloaded from a server, and a third for user data. Alternately you might have a case where you want some objects to be persisted while others can live in an in-memory store and do not need to be saved between uses of the app.