Introduction

FMTC uses a root and stores to structure its data.

There is generally a single root (which generally corresponds to a single backend), which contains multiple stores. Cached tiles can belong to multiple stores, which keeps duplication minimized.

The structures use the ambient backend when a method is invoked on it, not at construction time.

Therefore, it is possible to construct an FMTCStore/FMTCRoot (see below) before initialisation, but 'using' it will throw RootUnavailable.