World Structure and Dynamics

// A WORLD W consist of the 
//
// - WORLD structure GRIDSPC (for the spatial structure and the objects)
// - WORLD structure GRIDAUD (for the sound structure)
// - WORLD structure GRIDIMG (for an image structure) (optional)
// - a WORLD population POP
// - a WORLD INPUT BUFFER (WIB)
// - a WORLD FUNCTION wf()
//
// The GRIDSPC represents a 2-dimensional field  with (Y,X)-coordinates
// The GRIDAUD represents a 2-dimensional field parallel to the spatial GRID
// containing sounds emitted at that position
// The GRIDIMG represents a 2-dimensional field parallel to the spatial GRID
// containing images associated with the objects at that position
// The POP represents a list of all learning semiotic systems present in the GRID
// The WIB represents the planned actions of all LSSs in a list. 
// The wf() manages possible changes according to the actual GRID, the content
// of the WIB and according to some world laws.
//
// wf1 = newPOS o newMOVE o nmove o newSOUND
//
// The change of the images happens associated with the newMOVE or nmove operations