URL of the resource in case it must be fetched
Flag whether the resource reference should also be added to the spine with a 'linear=no' attribute
The item must have a fixed id, rather than a generated one
Media type of the resource; this must be added to the package manifest entry
Extra properties, defined by the package specification, to be added to the entry
The URL to be used within the EPUB; relative to the top of the file
Content of the resource in case it is generated by this program
Interface for the resources that, eventually, should be added to the EPUB file