C.2.3:4.3 - Extensibility and local anchors

FPF provides the default anchor ladder F0...F9. A context may define sub-anchors or intermediate anchors such as F4[OCL] or F6.5, but only if:

• global order is preserved,
• the local anchor is explicitly docked to a parent anchor,
• the context does not invent a rival ladder or proxy scale.