This defines a trim curve vertex. A trim curve vertex may be specified as a literal. All of its components are identified by position rather than by keywords. They are interpreted as
( u, v, w, t)
where:
| u and v | the parametric space coordinates of the trim curve vertex. | 
| w | the weight of the vertex. | 
| t | parametric distance in the space of the curve it helps describe. | 
The elements of a trim curve vertex must be literals. They may not be represented by expressions or variables.