A stiffened raft is a slab on the ground with edge beans and internal beams which are poured as an integral part of the slab.  This design is mainly used on stable sites, 
A raft slab involves digging trenches in a grid pattern into the ground and forming voids  with sand and stone dust, trench mesh  then gets placed into the channels creating an internal beams.
The Stiffened Raft Slab

Footing systems