LatticeXvl was an experimental parametric geometry approach that was not adopted into the X3D standard
but nevertheless demonstrates multiple extensibility techniques for integrating new capabilities.
The LatticeXvl examples
was integratable as a commercial extension within X3D.
This technique is repeatable.
The extension approach to XML validation has been maintained through each version of X3D,
and is documented further in the actual
X3D DTDs and Schemas.