Level transitions like in Disnored Thread

If any of you have played games like Dishonored, you'll know what I mean. I'm talking about an open world feeling, while a game still being linear. Dishonored uses different levels for different parts of the city (Distillery District, Flooded District, etc.) which you can travel back and forth between to. Now I was wondering, would there be any good way to do this with the Source engine? I'm mostly in doubt about making changes in the environment. (Something you do in one district changing something in another district, So basically an action-reaction system). Would I require to make a new copy of a district for every little change? That seems a bit unnecessary and could become cluttered. Or is there any way to program something, giving you full control of what will be loaded in the level you're going back to?

I realize I'm being a bit vague. Explaining my thoughts and ideas isn't too easy for me, but hopefully someone's out there who knows what I mean! (And more importantly, has a way to actually do this using a very efficient method)

With the way the source engine is now, I don't think you can do that. You would have to heavily modify the engine for this to work, including changing how maps work and function.

In UDK I can think of a few ways to do this including having several booleans that would trigger events in matinee or kismet after completing some quest or object. But you would have to pre-build all the instance changes into the map just hidden away until called on. This does require some scripting for Unreal but isn't nearly as much as would be needed for Source.

I don't use source, but every id engine since Quake 1 has the ability to do stuff like this more and more, so I'd bet Source can, Valve just didn't. In D3 tech it's as simple as passing values between maps & using those to change states of entities on the other level. In Q2 it's using triggers that are used on level change. Both can get more complex and I'm betting source can to. At the worst, you add some variables to the player's entity & have those checked on level load for deciding what should be done with the entities in the next map.

Just realized I made a really stupid typo. Oh well. Thanks for the quick response. I agree with the both of you. It'd be easier to do this in UDK is what I thought. Unfortunately I don't have any experience with Unreal (yet). I guess I'll just try some things out and see where it goes. Can always switch to UDK and start working with that. I've been planning that for some time now...