The default style extension for an MVF. A DefaultStyle has things like color, height and opacity and the geometry it should be applied to. It is geared towards rendering the MVF in a 3D mapping engine, but specific properties like color may be useful in other contexts.
If a geometry is NOT referenced by a style, or some other style-like extension, it should generally NOT be rendered by default.
In particular, it is expected that Geometry of kind area will not get a default style, but there may be other cases.
The default style extension for an MVF. This describes things like the color, height and opacity that should be applied to Geometry.
Not every geometry will have a default style, and if it does not, it should not be rendered.