Reservations about basing 'testAssertion' and 'shared' on common type

[Stephen Green <stephengreenubl@gmail.com>]

I have some reservations about using a common type in the
markup to make 'testAssertion' and 'shared' derive from the
same type (at least for those elements they have in common).
A major argument in favour of the common type is to reduce
redundancy. The argument against it which concerns me is
that this introduces a weak feature when W3C XML Schema
derivation (extension) is used. It adds complexity and may
be a cause for concern if we ever wanted to further extend the
types in another version. In principle there is no problem with
using extension; it's just a concern when this is done with
W3C XML Schema (as in TAML version 0.3). My opinion is
that if we continue to use W3C XML Schema to define TAML
we are better trying to avoid derivation more than we try to avoid
redundancy.
---
Stephen D Green