As was discussed in the introduction, a 3D graphics API should, at least in principle, be extendable to incorporate new graphics hardware features or algorithms that may become popular in the future. Although attainment of this goal may be difficult to gauge until long after the API is first in use, steps can be taken to help to achieve it. Orthogonality of the API is one element that helps achieve this goal. Another is to consider how the API would have been affected if features that were consciously omitted were added to the API.