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.

• Specifies the linear reading-order of the publication.
• Provides fallback information to use when unsupported extensions to OPS are employed.
• Provides a mechanism to specify a declarative table of contentsglobal navigation structure (the NCX).