Here is a temptative file format. It uses nesting. 

# a special tag WorldForge Map Format 1.0
AMF 0.1
# the object category format will be specified later on
Object Category DB
# the object DB format will be specified later on
# I think it's important to have a unique id for each object
# it can be either a number or a unique name
Object DB
# starting the map definition, Group is a special tag
# anything between Group and { is refered to as the unique id
Group MapName {
 Offset: X Y
 Ground {
   sizeX sizeY 
   defaultTile randomSeed
   # to override the default add as many tiles as you want
   # if you don't want a rectangular shape, add empty tiles
   Tile: tileid dX dY
   ...
   # then define the height of the center of every tile in the
   # rectangle in row order
   Height{
     Z00 Z01 Z02 ...
     Z10 Z11 Z22 ...
     ...
   }
   # or 
   Height {
     Fixed dZ
   }
 }
 Group Road{
   Tile: tileid dX dY
   ...
 }
 Group House {
   Offset: X Y
   Ground {
     sizeX sizeY
     defaultTile randomSeed
   }
   Group Walls {
     Object: objectid dX dY dZ
     ...
   }
   Group Kitchen {
     Offset: X Y
     Ground{
       size X sizeY
       defaultTile randomSeed
     }
     Group Table{
       Object: tableid dX dY dZ
       Group{
          Object: objectid dX dY dZ
          ...
       }
     }
   }

 

 

 
Explanations:

 
Group name {
    Offset
    ...
}       
        : creates a group, inside the group every dX dY dZ
        is an offset from the group's origin (0,0,0). A group can
        be nameless

 
Ground { ... } : defines the ground tiles for a group, only a ground
        tile can have a Z information. You can have height
        information inside a ground region. Note that you can have
        empty tiles to have non-rectangular areas. 

 
Tile: tileid dX dY
        a tile either goes on top of the ground or replaces a ground
        tile. There is no Z as this information is given by the Height
        information. The dX and dY in a tile is limited to tile
        positions, i.e. 1M scale

 
Object: objectid dX dY dZ
         An object is on top of the ground, so it needs the Z
         information

 

 

 

 
In the first implementation I don't know if we'll be able to support
multiple ground regions. i.e.

 
     +---+
     |   +----+
     |   +----+
     +---+

 

 
>From the file format, it is implied that an objectid can refer to a
group of objects, a random seed is used to choose the actual value.

 
Future extensions could be of the form of small scripts, i.e.
   Script Forest {
      sizeX sizeY      
      Loop dX dY {
         Place: treeid maxX maxY
      }
   }

 
where size(X,Y) is the size of the forest, dx dY is the number added
in X and Y after each loop iteration (i.e. same as a double for
loop) and maxX and maxY dictate the size of the rectangle in which the
tree can be randomly placed.
lavoie at zeus.genie.uottawa.ca