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C00002 00002	4.0	MEMORY  -  DATA STRUCTURES.
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4.0	MEMORY  -  DATA STRUCTURES.
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	   A. 	Representation of a Geometric Mental Universe.
	   B.	Contour-Region-Edge Image Representation.
	   C.	Semantic, Feature and Predicate Representation.
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	In order to get a computer to deal with the physical world it
must  have  a  data  representation  on  which computations involving
space, time, shape, size and the appearance of things can be done. In
this  section,  a  representation  for  the  topology,  geometry  and
photometry of everyday things is  explained.  The  data
structures  discussed  are  implemented  as  small  blocks  of  words
containing pointers and data in the fashion  usual  to  graphics  and
simulation;  an introduction to this technology can be found in Knuth
[1]; and although the language of implementation  is  PDP-10  machine
code,  the  data  and  functions  presented below are accessible from
higher level languages like LISP and ALGOL.

I.A. Representation of a Geometric Mental Universe.

	At the top of the data structure is a  single  universe  node
from  which  everything  else can be reached.   Immediately below the
universe node is a ring  of  world  models.   A  robot  dealing  with
physical world sensor input, such as video data, has one of its world
models dedicated to simulating  the  immediate  here  and  now;  this
mental  world  is  called the reality world model. In addition to the
reality world, a robot may have  fantasy  world  models  for  problem
solving, planning or for recalling platonic object prototypes. In the
following, a two world mental universe will be the most common,  with
the  reality world being referred to as a "map" and the fantasy world
being referred to as a "dictionary".

	Geometric world models have four  basic  kinds  of  nodes:
body, face, edge and vertex. The face, edge and vertex nodes are used
to form polyhedrons which may be attached to body nodes.  Body  nodes
in  turn  are  connected  to  each other in rings and trees to form a
world model. Additional kinds of nodes  discribe  cameras  and  light
sources  as  well  as  temporary  data  such  as shadows, spines, and
trajectories.

	The image data structure  presented  in  this  section  is  a
computer's  internal  notation  for  what  is  vulgarly called a line
drawing; the common term is misleading because it  does  not  suggest
the  equally  important  space between the lines; terms closer to the
idea would be "mosaic drawing" or "stained glass window drawing".

The  data  structure  has  main  levels:  TV  raster,  video
intensity contour, arc contour, and region-edge.
	...continuation of this section follows SAILON-71,