Three distinct frameworks support the EPUB document type:
- NCX - A declarative global navigation definition.
- OCF - The Open Container Format(OCF) defines a mechanism by which
all components of an Open Publication Structure(OPS) can be combined into a single
file-system entity.
- OPF: - The Open Packaging Format(OPF) defines the mechanism by
which all components of a published work conforming to the Open Publication Structure(OPS)
standard including metadata, reading order and navigational information are packaged into
an OPS Publication.