includes Geometry Constraint and Dimension. Constraint.
1.Geometry constraint control
the positional relationship between the objects.
Geometry constraint includes parallel,
perpendicular, horizontal, vertical, tangent, concentric,
coincident, equal, collinear, symmetrical and fixed constraints.
The valid entities for geometry constraint includes line,
circles (arcs), point.
2 Dimension constraint
control the object length, angle, radius and diameter.
Dimension includes linear dimension,
radial dimension, diameter dimension, angular dimension.