[whatwg] MetaExtensions for HTML5 vs. custom tagging

[Christine Smith]

Over the years, my company has developed custom IBM.xxx meta tags for our
internal and external web pages that are used by various internal tools. My
question has two parts:

1) Is there an allowance for custom taxonomy definition that is not a
proposal for general acceptance? For example, if we manage our own
company-specific meta data schema and linked our pages two it, would it
pass validation?  If so, is there a spec that shows how to create our own
schema?

2) The "Registered Extensions" table at
http://wiki.whatwg.org/wiki/MetaExtensions still show status of "proposal"
for all tags. Does that imply that they are not fully accepted as
extensions? For example,
-- I would like to know that Dublin Core is accepted, so that I can rely on
its continued support.
-- However, there are also redundant examples in that table (e.g.
web_author and designer) and tool-specific proposals that could be made
more generic for broader use (e.g. Web Trends wt.xxx could become
analytics.xxx).

Is there a timeline to update the status to "accepted" for those that will
be supported in the future?

Thanks for your advice.

Christine Smith
IBM