You are correct.  That fits the general definition of virtual domains.  
There is inherent confusion already with the overloaded word "virtual" as
it is used in postfix.  It would be nice if your directions would help
clarify some of the aspects.

That proves my point.  The statement is correct by itself, but that is not
really how virtual_maps are being used in your example.

Let me offer a suggestion, then.  In your example, make it very clear that
you are demonstrating sendmail-style virtual domains where every local
account exists in all of the domains accepted by postfix.  Your table has
headings "virtual address" and "real address".  It's not really the real
address.  It is the name of the local account where the email is
delivered.

In the event that users in one virtual domain should be distinct from
users in another virtual domain (i.e., d...@example.net is different from
d...@example.com) and no local accounts exist for addresses in the virtual
domain, then postfix-style virtual domains need to be used.

Here is an overall picture.  You have some of this in your directions. At
the top level, there are two types of virtual domains.  One is a
sendmail-style virtual domain (which you use) and the other is the
postfix-style virtual domain.

There are two types of postfix-style virtual domains.  There is the
"regular" virtual domain and the virtual mailbox domain.  Regular virtual
domains have no local mailboxes (real or virtual) associated with them.  
Consequently, virtual domains must eventually be mapped to an address
where the email can be delivered.  Virtual mailbox domains and their
addresses are associated with virtual mailboxes (i.e., not a local
account) on the local computer.

virtual_maps serves two functions.  It can map any address (real or
virtual) to any other address or addresses (real or virtual, local or
remote) regardless of any virtual domains (which is how you are using it).  
For postfix-style virtual domains, virtual_maps store what I call the
domain marker and the entries for _all_ of the addresses in that virtual
domain.  virtual_maps can used for both functions at the same time.

virtual_mailbox_maps stores the domain marker and the entries for _all_ of
the addresses in that domain that will be delivered to virtual mailboxes
on the local computer.  virtual_mailbox_maps might even contain specific
information about the virtual mailbox, including its path, its size limit
and the uid/gid it is using.

If the pieces appropriate to your configuration can be incorporated in
your directions, then you will have a complete example that people can
follow and understand when configuring sendmail-style virtual domains.

On a side note, I agree with a previous poster that I would not encourage
people to separate their various files by domain unless it was to keep
text files that would be combined to form a single hash file.

----
Russell Mosemann, Ph.D. * Computing Services * Concordia University, Nebraska
"There's a simple solution to every problem if you're just willing to
 implement it." - Mark Lemke