Isometric map data


I’ve read some articles and tutorials on the different file formats to store isometric map data. They are usually XML or text file. I am wondering what is the best way to store map data in an online game? I am working on a project where the players are able to customize their own maps and the stage area probably has a few hundred tiles.

Using a 2d array, the data may be quite large depending on complexity. I expect the players to customize their maps regularly and wonder how heavy that will be on the bandwidth. Is there a preferred way to store/compress these data so that it will be faster to load/save? Maybe only saving a particular change?

I can probably handle the loading/saving time with a waiting screen but I am hoping for speed. I am wondering how games like Restaurant City does it. It looks as if there is much to load and save but it does it all pretty fast.

Hope there’s some valuable advice someone could share.