[tei-council] Minimal TEI schema

[Lou Burnard]

We have abolished the distinction between base and additional tag sets. 
But we have retained the idea that a conformant document must have a 
header. This suggests that the minimal combination of modules needed for 
TEI conformance must include the header. Furthermore, if a conformant 
document must have a root of TEI or teiCorpus, we must include the 
textstructure module. Since every element (I think without exception) in 
those two modules makes use of at least one class defined by the TEI 
module, you won't get far without that. And it's hard to see how you can 
get by without at least one element from the Core module, though I am 
not quite so sure of that as I am of the others.

SO, today's question : should we state that a minimal requirement for 
TEI conformance is that the schema in question uses those four modules 
(header, textstructure, tei, core)?  I don't see that assertion spelled 
out in the current draft, though there is reference to "the TEI basic 
four modules" which is presumably the same thing.