[Yaml-core] #DOMAIN proposal (!\uses-domain)

[Clark C . E. <cc...@cl...>]

Over the last day or so somehow in an attempt to synronize
planned changes to the spec an off-list thread started.
Rather than forward the thread (which would be alot of spam)
I'm just going to post a summary of the relevant parts.
Let me start with Brian's #DOMAIN proposal.

On Wed, Aug 07, 2002 Brian Ingerson wrote:
| I've been rethinking the concept of a #DOMAIN directive. Since
| many (most?) documents will fall under a single domain, having a default
| domain specified upfront might be nice.
| 
|     --- #DOMAIN:foobar.com,2002
|     foo:
|       bar:
|         - !/tiddly xyz
|         # same as:
|         - !foobar.com,2002/tiddly xyz
|     ...
| 
| I know we can accomplish similar effect with !^tiddly, but I actually think
| the two forms compliment each other nicely. Of course, the default header
| would be:
| 
|     --- #YAML:1.0 #TAB:NONE #DOMAIN:yaml.org,2002
| 
| In other words, in the absence of the #DOMAIN directive, 
| !foo and !/foo would be the same.

When asked about how #DOMAIN differs from the ^ mechanism...

| The #DOMAIN is the default domain for !/foo. It is declared up front and
| cannot change. It is useful because most documents will fall mostly under one
| domain. Even when there are more, a default can still be handy. Doesn't XML
| set it's default namespace in the header?
|
| ^ is also useful, but isn't declared up front. Originally we wanted ^ to be
| scoped within a node and its children, which made sense, but we punted on
| complexity. ^ can also be changed within a document. ^ can also be used for
| any part of the URI, not just the domain.

I kinda like the idea.  Although I think !/foo should then be a
syntax error if #DOMAIN isn't present, as it probably would be
an oversight.  It does provide a limited way to have two active
"domain abbreviations" in effect as well.  

Question:  If we did something like this, do we still need ^ ?