[osis-core] reference elements in a separate schema for inclusion in other XML vocabluraries.

[Todd Tillinghast]

I will be attending the CBA meeting with Mike Perez in a couple of weeks
to promote and answer questions about OSIS.

I expect three types of uses for XML among the people at the meeting:
1) Encoding Bibles for which OSIS is a 100% fit.
2) Encoding related texts like sermons, Bible studies, etc... where OSIS
should be a good fit but we have not demonstrated a strong best
practices yet, but will improve that in Aug.
3) Encoding text that are really a better fit for other standards like
TEI, docBook, etc..., but could really benefit from our reference
mechanism.

For this third case we CAN provide the <header>, <work> (and children),
and <reference> elements along with the simple/complex types
osisRefType, osisIDType, and osisWorkType.

This would allow people to extend other schema to include references
(and if they wanted the osisID mechanism).

This could be accomplished with the current schema, but would be cleaner
for the group extending our reference mechanisms if there were a reduced
schema just for this purpose.  I am not necessarily suggesting that we
split the current schema.  We could create a second schema with only the
elements and types needed for extension.

Thoughts?

Todd