Thanks, excellent references to help me understand the ontology of the e-textbook within the Pressbook framework.
“TextbookHTML is a fork of OReilly Media’s HTMLBook for Docbook” appears to be focused on an academic context. I’m not sure what the value of forking is, compared to working to enhance the existing HTMLBook spec. Forking can be beneficial, as in LibreOffice, or detrimental for OpenOffice in loss of resource talent.
The Metadata Handbook “presents an overview of metadata’s role in the publisher supply chain.” It is more focused on a commercial context than an open source textbook perspective. However, the metadata system model brings general awareness to the advantages and importance of connective semantics to digital information communications.