S-images contain both primitive and complex elements. Primitive elements are the smallest units of a picture. All visual representations are made of combinations of these elements. Visual Instantiation is turning a non-visual representation into a visual one.
Two ideas should be associated with a visual abstraction only if the inferences the agent can make and actions the agent can do with the abstraction can also be done to the referents of the ideas themselves. Said another way, the abstraction captures visual similarities of the their referents that are relevant to simulation and manipulation.
| Table 3 | |||||
| Primitive Element name | attributes | ||||
| polygon | location, size | ||||
| rectangle | location, size, height, width, orientation | ||||
| triangle | location, size, height, width, orientation | ||||
| ellipse | location, size, height, width, orientation | ||||
| circle | location, size, height | ||||
| arrow | location, length, start-point, end-point, thickness | ||||
| line | location, length, start-point, end-point, thickness | ||||
| point | location | ||||
| curve | location, start-point, mid-point, end-point, thickness | ||||
| text | location, length, letters | ||||
Table 3 shows a list of the primitive elements.
The primitive elements are organized into a two-tiered hierarchy. Rectangle and triangle are subclasses of polygon; circle is a subclass of ellipse.