  This document describes an XML encoding standard for metadata about services
implementing the table access protocol TAP [TAP], referred to as TAPRegExt.
Instance documents are part of the service's registry record or can be obtained
from the service itself. They deliver information to both humans and software
on the languages, output formats, and upload methods supported by the service,
as well as data models implemented by the exposed tables, optional language
features, and certain limits enforced by the service.
