The optional size attribute defines a recommended size for visualization of an infinite drawable element such as plane, cylinder, axis, etc., or objects without explicit geometric parameters (e.g. coordinate system).
The optional tolerance attribute specifies the maximum distance from the vertex underlying geometry (3D point) to the ends of all the adjacent edges that are terminated in the neighborhood of this vertex. This value can be defined only for the case of the tolerant body.
The optional transparency attribute defines the transparency property of a model entity.
Source
<xs:element name="Vertex" type="VertexType"><xs:annotation><xs:documentation>The global Vertex element is a topological entity which lies at a 3D point and normally is used to bound an edge.</xs:documentation></xs:annotation></xs:element>