"Completeness" as a feature of a POW (aka EPUB+Web)??

In rewriting the document about Portable Documents for the web (thanks for the suggestion & link, Tzviya), I can across the following paragraph:

EPUB can be viewed as simply defining a specialization of Web content that assures that a collection of content items has the needed properties of completeness and logical structure, and does so in a standard way that other processing tools and services can reliably create, manipulate, and present such collections. This completeness constraint is key for bridging the current gap between an online and offline/portable view of the same content (see <a href="#whynow">section on usage patterns</a> below).

While not spelled out here or in the “section on usage patterns”, I am going to take the terminology of “completeness” to mean “fully self-contained” (aka no external references).  If it means something else, feel free to ignore what follows (but only after you correct me :).

In the current use cases for EPUB (books, magazines, etc.), the desire by the publisher to have everything contained inside the package is clearly key – just as that same property has been a tenant of the various PDF subset standards (PDF/A, PDF/X, etc.)  However, there also exists for PDF use cases where external references are a key aspect to the workflow – for example, external content or color profiles in a variable or transactional workflow (eg. PDF/VT).   As such, I would like to suggest that as a portable document for OWP, that there also needs to be a provision for external references in this POW (Portable Open Web) format.

I know that there have been discussions about this around EPUB in the past for large assets (eg. Video and audio), but I would put forth that the same principles could also be applied for other types of content as well.  Be it advertisements in a publication, current data sets in a STEM publication or even just a reference to the latest version of a common JS library used by the publication.

What do others think about this?   Is completeness/self-contained a requirement in a POW?

Thanks,
Leonard