It's really simple. This was my first App Engine project. There's only one model, Tile, that has contents, namespace, and x/y coordinates. The contents field is a string representing the text in this tile. The namespace tells you what page the tile belongs to (e.g., /newsyc), and the coordinates are relative to the starting position. Namespace, x, and y are part of the keyname, so contents is the only model property. I don't create a tile until someone writes to that area.

I don't want to use cookies, but I'm thinking about implementing some kind of directions feature. ("Where am I?" "How do I get to X?") But I also want to keep the system really simple, so I don't know.