[Yaml-core] Tagging issue

[Oren Ben-K. <or...@be...>]

The following issue has been raised before as part of the great %TAG 
debate. It was a minor point so it got lost amongst the bigger issues. 
Working on the being-updated spec examples, I stumbled on it again, and 
I'd like to reconsider it in the context of the current %TAG rules 
(which I am explicitly _not_ reopening, thank you very much :-)

The issue is:

It is not unusual for a document to use just a single tag for the root 
node - in fact, I believe this will be the most common way explicit 
tagging will be used, as usually all other tags can be resolved from 
the path to and/or content of the nodes. The root node's tag serves as 
"the" way to associate a "schema" with the whole document - the 
Archimedes point one can infinitely leverage.

However, under the current rules, this is somewhat awkward to specify. 
Consider:

 %TAG !handle! tag:my.domain.com,2002:/namespace/
 --- !handle!document-type
 # Document content here, no specified tags,
 foo : bar
 ...

It would have been nicer to be able to simply write:

 --- !tag:my.domain.com,2002:/namespace/document-type
 # Document content here, no specified tags,
 foo : bar
 ...

For this to work, the current rules need to be modified in the following 
way:

- Local (private) tags may not begin with "!<word>:[^:]".
- A tag beginning with "!<word>:[^:]" is assumed to be a URI.

The "[^:]" (not ":") requirement allows languages that use "::" for 
namespace separation to specify tags such as "!Date::Roman".

Anyone feel strongly against adding this rule?

Have fun,

 Oren Ben-Kiki