My question is on the
<dc:identifier>. Is the
<dc:indentifier> unique and hashed to an IP address or MAC address?
As long as the identifier is unique, it should be fine. At the above link, the IDPF says:
Every metadata section must include at least one identifier element containing an unambiguous identifier for the Publication. Multiple identifier elements are permitted, but only one can be marked as the Unique Identifier via the package element unique-identifier attribute.
Yes it should be unique, and no, it is not hased to an IP or MAC address.
4 in the position directly after the second
- indicates that it is a random UUID. The UUID linked to a MAC address is version 1.
There is however, no necessity that this is a UUID. The only premise is that
a primary identifier that is unique to one and only one particular EPUB Publication
E.g. the epub 3 examples mostly use a URN, and AFAIK none of those use an ISBN.