Save input from interactive forms

As a braille user filling out an interactive form, I would like to be able to save the entered information so that it is available when I next open the file, or when I send it to someone else.
Detail
This relates to #59. The specification should have a defined method for saving entered input so that it can be kept with the document, and kept available when the file is closed and later re-opened.
Proposal
The information could be stored in a file that is placed in the EBRF package alongside the document, and reference the related form fields. This would keep the entered information separate from the document, and make it easy to remove it if desired. Form fields would need to have identifiers that are unique across all files in the EBRF package if the complete document is made up of several files, such as by referencing their file name along with a unique identifier in the file.