For saving files I was going to use the Boost serialization stuff, this is where the relevant classes define a single serialization method which takes an Archive which it them typically passes down to the classes components. The thing is you have two different contexts in which you want to save a class, when the content is first being designed in some kind of tool and when the contents have changed because of the players actions and the changes need to be saved. So your classes could have two separate serialize methods for saving their entire state and saving only their mutable state, or some other way of doing things. I think you'd want this to be designed from the outset to be as transparent and robust as possible, since any kind of save game corruption is a bit of a deal breaker for an rpg. Seems like rpgs are particularly difficult since you have so much to keep track of. Say in an RPG you have an Area class, which has contents like creatures, triggers and so on which can change, creatures can be killed, triggers can be fired, and also things like it's tile map and walk mesh which can't be changed. The player also needs to be able to go to an area, change something, go to another area and then save their game. So one way you could do things is make it so that when the player loads their save game the mutable contents of all the areas they have visited are all loaded into memory and stay their at all times before being written back again when they save their game. Is that typical, or is it more likely that stuff has to be written to temporary files?

Interesting thanks. I can see the idea of a "change log" type object could be useful, I'll have a think about it. I'm not sure I'd want to tie it directly to quests, I wasn't planning on having a quest object as such, but implementing them through a lose collection of scripts, dialogs and triggers.