Version metadata

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In many cases, I have several revisions of the same file, each one with few additions.
What is the best metadata to use to describe the revision?
I am looking for something like revision number in software that when I do a minor change in the software, I add one to the minor number.

Versioning metadata was actually in the original proposal for the EPUB 3 package document, but was removed during the revision as versioning was decided to be too producer-specific (everyone has their own internal processes and their own major/mid/minor numbering). I was kind of sad that we didn't leave in even an underspecified property in for those who wanted it, but I understand the confusion and potential duplication it would have caused.

The unique identifier combination of ID and modified timestamp is used to distinguish one EPUB from another, but for your own production purposes you'll need to insert your own version property into the package and/or content document metadata, depending on which type of file you're referring to

Unfortunately, I don't know of a widely-used version property, and dc:identifier is not a best fit with versioning. Schema.org does define a version field for CreativeWorks, but you'd need to create a prefix to use it in the package (e.g., prefix="schema: http://schema.org/CreativeWork#" and then <meta property="schema:version">1.0.1</meta>). You couldn't fully define the same in a content document, as RDFa Lite/microformats are not supported yet in EPUB 3.

If you don't want to go through the business of creating a custom prefix, you might get away with using the EPUB 2 meta element:

<meta name="version" content="1.0.1"/>

It's perhaps not completely in the spirit of the specification to use this element (it's for forwards compatibliity in EPUB 2), but I don't think this is a violation, either, since the metadata is not for the reading system, and the EPUB 2 meta element must be ignored by EPUB 3 reading systems. You could do similar in content documents, since this is also the HTML syntax.

Sorry s/microformats/microdata/ in the above. Too many micro things these days... :)

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